Compositions and methods for treating a substrate and treated substrates

Abstract

Disclosed herein is an aqueous treatment composition comprising an acid, such as a fluorometallic acid, and a fluoride salt. Further disclosed in a pretreatment composition comprising an acid, a source of a metal, a source of free fluoride, and an aqueous medium. Also disclosed are methods of treating metal substrates, treated metal substrates, and kits.

Description

COMPOSITIONS AND METHODS FOR TREATING A SUBSTRATE AND TREATED SUBSTRATES FIELD

[0001] The present disclosure relates to compositions and methods for treating a substrate as well as treated substrates. BACKGROUND

[0002] The use of protective coatings on metal substrates for improved corrosion resistance. In addition to disrupting the integrity of the metal substrate, corrosion also poses problems for metal substrates used in electrical current transmission because corrosion products increase the resistance of the metal substrate at the substrate surface. For example, porous titanium metal is commonly used as a current collector in proton exchange membrane (PEM) electrolyzers and is coated with precious metals (such as platinum, iridium, or gold) by physical vapor deposition or electroplating to prevent growth of an insulating TiO2 layer that increases internal device resistance and limits hydrogen production capabilities. However, precious metals are expensive and physical vapor deposition requires use of a high-vacuum environment. SUMMARY

[0003] Disclosed herein is an aqueous treatment composition comprising more than 0.0% by weight and up to 28% by weight of a fluorometallic acid, based on the total weight of the composition; and a fluoride salt, wherein the fluoride salt is a different component than the fluorometallic acid; wherein the aqueous treatment composition comprises less than 30% by weight nitric acid, based on the total weight of the composition.

[0004] Further disclosed herein is a method of treating a metal substrate comprising contacting at least a portion of the metal substrate with the aqueous treatment composition disclosed herein.

[0005] Further disclosed herein is a metal substrate treated according to the method of treating a metal substrate disclosed herein.

[0006] Further disclosed herein is a pretreatment composition comprising: an acid; a source of a metal comprising vanadium, manganese, nickel, silicon, ruthenium, rhodium, palladium, gold, tin, tantalum, tungsten, iridium, silver, mercury, thallium, lead, bismuth, polonium, platinum, niobium, titanium, cerium, or a combination thereof; a source of freefluoride; and an aqueous medium, wherein the acid, the source of a metal, and the source of free fluoride are each different components.

[0007] Further disclosed herein is a metal substrate treated by a method comprising contacting at least a portion of the metal substrate with the aqueous treatment composition disclosed herein and contacting at least a portion of the metal substrate with the pretreatment composition disclosed herein.

[0008] Further disclosed is a kit comprising: the aqueous treatment composition disclosed herein and / or the pretreatment composition disclosed herein, and optionally instructions for treating a substrate with the aqueous treatment composition, the pretreatment composition, or both the aqueous treatment composition and the pretreatment composition. BRIEF DESCRIPTION OF THE FIGURES

[0009] Figure 1 shows an isometric view of an aperture of a portion of an expanded metal mesh porous metal substrate.

[0010] Figure 2 is SEM images of chemically pure grade-1 titanium foil: A) before, and B) after treatment.

[0011] Figure 3 is a bar graph showing contact angle of water and diiodomethane of the titanium surface before and after exposure to the treatment solution.

[0012] Figure 4 is a graph showing grazing incidence X-ray diffraction pattern of untreated and treated titanium foil, highlighting the change in relative (002) and (101) reflection intensity.

[0013] Figure 5 is a bar graph showing interfacial contact resistivity (ICR) data of untreated and treated titanium foils after the listed exposure time to 2.4 V vs. NHE in pH 3 sulfuric acid.

[0014] Figure 6 is SEM images of chemically pure grade-1 titanium foil exposed to 2.4 V vs. NHE in pH 3 sulfuric acid for 250 h: A) without and B) with treatment.

[0015] Figure 7 is a bar graph showing interfacial contact resistivity (ICR) data of untreated and treated titanium foils after 1 hour exposure to 400°C.

[0016] Figure 8 is a graph showing TOF-SIMs depth profile for H+ / Ti+relative ion intensity of titanium foil and two treated titanium samples.

[0017] Figure 9 is a graph showing TOF-SIMs depth profile for Na+ / Ti+relative ion intensity of titanium foil and two treated titanium samples.

[0018] Figure 10 is a bar graph showing interfacial contact resistivity (ICR) growth rate over 50 hours of electrolysis at 2.4 V vs. NHE in pH 3 sulfuric acid of various titanium foils exposed to 3.4 wt.% ammonium bifluoride with the listed co-acids.

[0019] Figure 11 shows XRF spectra of the titanium substrate treated with only the first treatment solution (dotted) compared to the substrate further treated with the niobium-containing pretreatment composition (solid). The two vertical lines indicate the Kα1 and Kα2 of Nb signal.

[0020] Figure 12 shows XRF spectra of Pt coated Ti foil compared with bare Ti foil without coating (dashed line).

[0021] Figure 13 shows top-down SEM images of a titanium foil treated with a platinum solution.

[0022] Figure 14 shows XRF spectra of Pt coated Ti foil compared with bare Ti foil without coating (dashed line).

[0023] Figure 15 shows top-down SEM images of a titanium foil treated with a platinum solution.

[0024] Figure 16 shows interfacial contact resistance growth rate on a logarithmic scale of titanium foils treated under the listed conditions that have been exposed to 2.4 V vs NHE in pH 3 sulfuric acid for 100 h.

[0025] Figure 17 shows XRF spectra of Pt coated Ti foil where the Pt coating was applied with current assistance.

[0026] Figure 18 shows top-down SEM images of a titanium foil treated with a platinum solution applied with current assistance.

[0027] Figure 19 shows XRF spectra of Au coated Ti foil. DETAILED DESCRIPTION

[0028] For purposes of the following detailed description, it is to be understood that the disclosure may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers such as those expressing values, amounts, percentages, ranges, subranges and fractions may be prefaced by the word “about,” even if the term does not expressly appear. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present disclosure. At the very least, and not as an attempt tolimit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Where a closed or open-ended numerical range is described herein, all numbers, values, amounts, percentages, subranges and fractions within or encompassed by the numerical range are to be considered as being specifically included in and belonging to the original disclosure of this application as if these numbers, values, amounts, percentages, subranges and fractions had been explicitly written out in their entirety.

[0029] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.

[0030] As used herein, unless indicated otherwise, a plural term can encompass its singular counterpart and vice versa, unless indicated otherwise. For example, although reference is made herein to “an” acid and “a” fluoride salt, a combination (i.e., a plurality) of these components can be used.

[0031] In addition, in this application, the use of “or” means “and / or” unless specifically stated otherwise, even though “and / or” may be explicitly used in certain instances.

[0032] As used herein, “including,” “containing” and like terms are understood in the context of this application to be synonymous with “comprising” and are therefore open-ended and do not exclude the presence of additional undescribed or unrecited elements, materials, ingredients, or method steps. Nevertheless, they also include the more restrictive terms “consisting of” and “consisting essentially of.” As used herein, “consisting of” is understood in the context of this application to exclude the presence of an unspecified element, ingredient, or method step. As used herein, “consisting essentially of” is understood in the context of this application to include the specified elements, materials, ingredients, or method steps “and those that do not materially affect the basic and novel characteristic(s)” of what is being described.

[0033] As used herein, the terms “on,” “onto,” “applied on,” “applied onto,” “formed on,” “deposited on,” “deposited onto,” mean formed, overlaid, deposited, or provided on but not necessarily in contact with the surface. For example, a coating composition “applied onto” asubstrate does not preclude the presence of one or more other intervening coating layers of the same or different composition located between the coating composition and the substrate.

[0034] As used herein, a “salt” refers to an ionic compound made of metal cations and non-metal anions and having an overall electrical charge of zero. Salts may be hydrated or anhydrous.

[0035] As used herein, “composition” refers to a solution or dispersion and “aqueous composition” refers to a composition in an aqueous medium that comprises predominantly water. For example, the aqueous medium may comprise water in an amount of more than 50 wt.%, or more than 60 wt.%, or more than 70 wt.%, or more than 80 wt.%, or more than 90 wt.%, or more than 95 wt.% based on the total weight of the medium. That is, the aqueous medium may for example consist substantially of water.

[0036] As used herein, the term “dispersion” refers to a two-phase transparent, translucent, or opaque system in which particles, such as metal particles, are in the dispersed phase and an aqueous medium, which includes water, is in the continuous phase.

[0037] As used herein, “treatment composition” or “aqueous treatment composition” refers to a composition that is capable of reacting with and chemically altering the substrate surface to afford corrosion protection.

[0038] As used herein, “treatment bath” refers to an aqueous bath containing the aqueous treatment composition and that may contain components that are byproducts of the process.

[0039] As used herein, the terms “Group IIIA metal” and “Group IIIA element” refer to an element that is in Group IIIA of the CAS version of the Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rdedition (1983), corresponding to Group 3 in the actual IUPAC numbering.

[0040] As used herein, the term “Group IIIA metal compound” refers to compounds that include at least one element that is in Group IIIA of the CAS version of the Periodic Table of the Elements.

[0041] As used herein, the terms “Group IVA metal” and “Group IVA element” refer to an element that is in Group IVA of the CAS version of the Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rdedition (1983), corresponding to Group 14 in the actual IUPAC numbering.

[0042] As used herein, the terms “Group IVA metal compound” refer to compounds that include at least one element that is in Group IVA of the CAS version of the Periodic Table of the Elements.

[0043] As used herein, the terms “Group IVB metal” and “Group IVB metal element” refer to an element that is in Group IVB of the of the CAS version of the Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rdedition (1983), corresponding to Group 4 in the actual IUPAC numbering.

[0044] As used herein, the term “Group IVB metal compound” refers to compounds that include at least one element that is in Group IVB of the CAS version of the Periodic Table of the Elements.

[0045] As used herein, the terms “Group VIII metal” and “Group VIII element” refer to an element that is in Group VIII of the CAS version of the Periodic Table of the Elements as is shown, for example, in the Handbook of Chemistry and Physics, 63rdedition (1983), corresponding to Groups 8-10 in the actual IUPAC numbering.

[0046] As used herein, the term “Group VIII metal compound” refers to compounds that include at least one element that is in Group VIII of the CAS version of the Periodic Table of the Elements.

[0047] As further defined herein, ambient conditions generally refer to room temperature (23°C) and humidity conditions or temperature and humidity conditions that are typically found in the area in which the aqueous treatment composition is being applied to a substrate, e.g., at ambient temperature (e.g., 10ºC to 40ºC) and 5% to 80% relative humidity, while slightly thermal conditions are temperatures that are slightly above ambient temperature.

[0048] As used herein, unless indicated otherwise, the term “substantially free” means that a particular material is not purposefully added to a mixture or composition, respectively, and is present only as an impurity in a trace amount of 5 ppm or less based on a total weight of the mixture or composition, respectively. As used herein, unless indicated otherwise, the term “essentially free” means that a particular material is present only in an amount of 1 ppm or less based on a total weight of the mixture or composition, respectively. As used herein, unless indicated otherwise, the term “completely free” means that a mixture or composition, respectively, does not comprise a particular material, i.e., the mixture or composition comprises1 ppb of such material, or that such material is below the detection limit of common analytical techniques.

[0049] Unless indicated otherwise, as used herein, the terms “total composition weight,” “total weight of a composition,” or similar terms refer to the total weight of all ingredients being present in the respective composition including any carriers and solvents.

[0050] As used herein, the term “halogen” refers to any of the elements fluorine, chlorine, bromine, iodine, and astatine of the CAS version of the Periodic Table of the Elements, corresponding to Group VIIA of the periodic table.

[0051] As used herein, the term “halide” refers to compounds that include at least one halogen.

[0052] As used herein, the term “mole ratio” means the ratio between the amounts in moles of any two elements contained in a molecule.

[0053] As mentioned above, the present disclosure is directed to an aqueous treatment composition comprising an acid, such as a fluorometallic acid, and a fluoride salt, wherein the fluoride salt is a different component than the fluorometallic acid, such as ammonium bifluoride.

[0054] The fluorometallic acid may comprise fluoride and a Group IIIA metal, Group IVA metal, Group IVB metal, a Group VI metal, and / or Group VIII metal.

[0055] The fluoride in the fluorometallic acid may have a mole ratio to the Group IIIA metal, Group IVA metal, Group IVB metal, Group VI metal, and / or Group VIII metal of more than 4. That is, for each metal atom present in the fluorometallic acid, there may be more than 4 fluoride atoms present in the fluorometallic acid. Non-limiting examples of fluorometallic acids comprising fluoride having a mole ratio of more than 4 include hexafluorosilicic acid, hexafluorozirconic acid, hexafluoroferric acid, hexafluoroaluminic acid, hexafluorotitanic acid, or combinations thereof.

[0056] The Group IIIA metal of the fluorometallic acid may, for example, comprise aluminum and may be provided in the aqueous treatment composition in the form of specific compounds of the Group IIIA metal, such as their soluble acids and / or salts. Examples of useful compounds include hexafluoroaluminic acid.

[0057] The Group IVA metal of the fluorometallic acid may, for example, comprise silicon such as silanes, silicas, silicates, and the like. The Group IVA metal may be provided in the aqueous treatment composition in the form of specific compounds of the metals, such as theirsoluble acids and / or salts. Examples of useful compounds include fluorosilicic acid, ammonium and alkali metal fluorosilicates, and the like, including by way of non-limiting example, hexafluorosilicic acid.

[0058] The Group IVB metal of the fluorometallic acid may comprise zirconium, titanium, hafnium, or combinations thereof. For example, the Group IVB metal used in the aqueous treatment composition may be a compound of zirconium, titanium, hafnium, or a mixture thereof. Suitable compounds of the fluorometallic acid include, but are not limited to, hexafluorozirconic acid, zirconium tetrafluoride, fluorotitanic acid, fluoro-hafnium acid and salts thereof.

[0059] The Group VIII metal of the fluorometallic acid may, for example, comprise iron and may be provided in the aqueous treatment composition in the form of specific compounds of the metals, such as their soluble acids and / or salts. Examples of useful compounds include hexafluoroferric acid.

[0060] The fluorometallic acid may be present in an amount of at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight, such as at least 4% by weight, such as at least 5% by weight, such as at least 10% by weight, such as at least 15% by weight, such as at least 20% by weight, such as at least 25% by weight, based on the total weight of the composition. The fluorometallic acid may be present in an amount up to 28% by weight, such as up to 25% by weight, such as up to 20% by weight, such as up to 15% by weight, such as up to 10% by weight, such as up to 7% by weight, such as up to 5% by weight, based on the total weight of the composition. The fluorometallic acid may be present in an amount of 0.5% to 28% by weight, such as 0.5% to 25% by weight, such as 0.5% to 20% by weight, such as 0.5% to 15% by weight, such as 0.5% to 10% by weight, such as 0.5% to 7% by weight, such as 0.5% to 5% by weight, such as 1% to 28% by weight, such as 1% to 25% by weight, such as 1% to 20% by weight, such as 1% to 15% by weight, such as 1% to 10% by weight, such as 1% to 7% by weight, such as 1% to 5% by weight, such as 2% to 28% by weight, such as 2% to 25% by weight, such as 2% to 20% by weight, such as 2% to 15% by weight, such as 2% to 10% by weight, such as 2% to 7% by weight, such as 2% to 5% by weight, such as 3% to 28% by weight, such as 3% to 25% by weight, such as 3% to 20% by weight, such as 3% to 15% by weight, such as 3% to 10% by weight, such as 3% to 7% by weight, such as 3% to 5% by weight, such as 4% to 28% by weight, such as 4% to 25% by weight, such as 4% to 20% byweight, such as 4% to 15% by weight, such as 4% to 10% by weight, such as 4% to 7% by weight, such as 4% to 5% by weight, such as 5% to 28% by weight, such as 5% to 25% by weight, such as 5% to 20% by weight, such as 5% to 15% by weight, such as 5% to 10% by weight, such as 5% to 7% by weight, such as 10% to 28% by weight, such as 10% to 25% by weight, such as 10% to 20% by weight, such as 10% to 15% by weight, such as 15% to 28% by weight, such as 15% to 25% by weight, such as 15% to 20% by weight, such as 20% to 28% by weight, such as 20% to 25% by weight, such as 25% to 28% by weight, based on the total weight of the composition.

[0061] In other examples, the aqueous treatment composition may be substantially free, or, in some cases, essentially free, or in some cases, completely free of any Group IVB metals.

[0062] The aqueous treatment composition further comprises a fluoride salt. The fluoride salt is different than the fluorometallic acid. Non-limiting examples of the fluoride salt include ammonium and alkali metal fluorides, such as ammonium bifluoride, potassium fluoride, sodium fluoride, and the like.

[0063] The fluoride salt may be present in an amount of at least 0.1% by weight, based on the total weight of the composition, such as at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight. The fluoride salt may be present in an amount up to the solubility limit of the fluoride salt, such as no more than 38% by weight, based on the total weight of the composition, such as no more than 20% by weight, such as no more than 15% by weight, such as no more than 10% by weight, such as no more than 7% by weight, such as no more than 5% by weight, such as no more than 4% by weight, such as no more than 3.5% by weight. The fluoride salt may be present in an amount of 0.1% to 38% by weight, such as 0.1% to 20% by weight, based on the total weight of the composition, such as 0.1% to 15% by weight, such as 0.1% to 10% by weight, such as 0.1% to 7% by weight, such as 0.1% to 5% by weight, such as 0.1% to 4% by weight, such as 0.1% to 3.5% by weight, such as 0.5% to 38% by weight, such as 0.5% to 20% by weight, such as 0.5% to 15% by weight, such as 0.5% to 10% by weight, such as 0.5% to 7% by weight, such as 0.5% to 5% by weight, such as 0.5% to 4% by weight, such as 0.5% to 3.5% by weight, such as 1% to 38% by weight, such as 1% to 20% by weight, such as 1% to 15% by weight, such as 1% to 10% by weight, such as 1% to 7% by weight, such as 1% to 5% by weight, such as 1% to 4% by weight, such as 1% to 3.5% by weight, such as 2% to 38% by weight, such as 2% to 20% by weight, such as 2% to 15% byweight, such as 2% to 10% by weight, such as 2% to 7% by weight, such as 2% to 5% by weight, such as 2% to 4% by weight, such as 2% to 3.5% by weight, such as 3% to 38% by weight, such as 3% to 20% by weight, such as 3% to 15% by weight, such as 3% to 10% by weight, such as 3% to 7% by weight, such as 3% to 5% by weight, such as 3% to 4% by weight, such as 3% to 3.5% by weight.

[0064] The aqueous treatment composition may comprise total fluoride in an amount of at least 50 ppm, such as at least 75 ppm, such as at least 100 ppm, based on total weight of the aqueous treatment composition. The aqueous treatment composition may comprise total fluoride in an amount of no more than 230,000 ppm, such as no more than 100,000 ppm, such as no more than 50,000 ppm, such as no more than 5,000 ppm, such as no more than 3,000 ppm, such as no more than 2,500 ppm, based on total weight of the aqueous treatment composition. The aqueous treatment composition may comprise total fluoride in an amount of 50 ppm to 230,000 ppm, such as 50 ppm to 100,000 ppm, such as 50 ppm to 50,000 ppm, such as 50 ppm to 5,000 ppm, such as 75 ppm to 230,000 ppm, such as 75 ppm to 100,000 ppm, such as 75 ppm to 50,000 ppm, such as 75 ppm to 3,000 ppm, such as 100 ppm to 230,000 ppm, such as 100 ppm to 100,000 ppm, such as 100 ppm to 50,000 ppm, such as 100 ppm to 2,500 ppm, based on total weight of the aqueous treatment composition. The total fluoride may be calculated by comparing the weight of the fluoride supplied in the aqueous treatment composition with the total weight of the aqueous treatment composition.

[0065] The composition may comprise free fluoride. In examples, the free fluoride may be derived from the fluoride-containing compounds described above and / or the free fluoride may be derived from a compound or complex other than a fluorometallic compound. As used herein, “free fluoride” refers to fluoride present in the aqueous treatment composition that is not bound to metal ions or hydrogen ions, as measured in parts per million of fluoride. Free fluoride may be measured using, for example, an Orion Dual Star Dual Channel Benchtop Meter equipped with a fluoride ion selective electrode (“ISE”) available from Thermoscientific, the sympHony® Fluoride Ion Selective Combination Electrode supplied by VWR International, or similar electrodes. See, e.g., Light and Cappuccino, Determination of fluoride in toothpaste using an ion-selective electrode, J. Chem. Educ., 52:4, 247-250, April 1975. The fluoride ISE may be standardized by immersing the electrode into solutions of known fluoride concentration and recording the reading in millivolts, and then plotting these millivolt readings in a logarithmicgraph. The millivolt reading of an unknown sample can then be compared to this calibration graph and the concentration of fluoride determined. Alternatively, the fluoride ISE can be used with a meter that will perform the calibration calculations internally and thus, after calibration, the concentration of the unknown sample can be read directly.

[0066] The free fluoride may be present in the aqueous treatment composition in an amount of at least 2 ppm, such as at least 10 ppm, such as at least 25 ppm, such as at least 35 ppm, such as at least 100 ppm, such as at least 200 ppm, based on total weight of the aqueous treatment composition. The free fluoride may be present in the aqueous treatment composition in an amount of no more than 230,000 ppm, such as no more than 100,000 ppm, such as no more than 50,000 ppm, such as no more than 5,000 ppm, such as no more than 2,500 ppm, such as no more than 2,000 ppm, such as no more than 1,500 ppm, such as no more than 1,000 ppm, such as no more than 600 ppm, such as no more than 200 ppm, such as no more than 100 ppm, such as no more than 75 ppm, based on total weight of the aqueous treatment composition. The free fluoride may be present in the aqueous treatment composition in an amount of 2 ppm to 230,000 ppm, such as 2 ppm to 100,000 ppm, such as 2 ppm to 50,000 ppm, such as 2 ppm to 5,000 ppm, such as 2 ppm to 2,500 ppm, such as 2 ppm to 2,000 ppm, such as 2 ppm to 1,500 ppm, such as 2 ppm to 1,000 ppm, such as 2 ppm to 600 ppm, such as 2 ppm to 200 ppm, such as 2 ppm to 100 ppm, such as 2 ppm to 75 ppm, such as 10 ppm to 230,000 ppm, such as 10 ppm to 100,000 ppm, such as 10 ppm to 50,000 ppm, such as 10 ppm to 5,000 ppm, such as 10 ppm to 2,500 ppm, such as 10 ppm to 2,000 ppm, such as 10 ppm to 1,500 ppm, such as 10 ppm to 1,000 ppm, such as 10 ppm to 600 ppm, such as 10 ppm to 200 ppm, such as 10 ppm to 100 ppm, such as 10 ppm to 75 ppm, such as 25 ppm to 100,000 ppm, such as 25 ppm to 50,000 ppm, such as 25 ppm to 5,000 ppm, such as 25 ppm to 2,500 ppm, such as 25 ppm to 2,000 ppm, such as 25 ppm to 1,500 ppm, such as 25 ppm to 1,000 ppm, such as 25 ppm to 600 ppm, such as 25 ppm to 100 ppm, such as 25 ppm to 75 ppm, such as 35 ppm to 100,000 ppm, such as 35 ppm to 50,000 ppm, such as 35 ppm to 5,000 ppm, such as 35 ppm to 2,500 ppm, such as 35 ppm to 2,000 ppm, such as 35 ppm to 1,500 ppm, such as 35 ppm to 1,000 ppm, such as 35 ppm to 600 ppm, such as 35 ppm to 200 ppm, such as 35 ppm to 100 ppm, such as 35 ppm to 75 ppm, such as 100 ppm to 100,000 ppm, such as 100 ppm to 50,000 ppm, such as 100 ppm to 5,000 ppm, such as 100 ppm to 2,500 ppm, such as 100 ppm to 2,000 ppm, such as 100 ppm to 1,500 ppm, such as 100 ppm to 1,000 ppm, such as 100 ppm to 200 ppm, such as 200 ppm to 100,000 ppm, such as 200 ppmto 50,000 ppm, such as 200 ppm to 5,000 ppm, such as 200 ppm to 2,500 ppm, such as 200 ppm to 2,000 ppm, such as 200 ppm to 1,500 ppm, such as 200 ppm to 1,000 ppm, such as 200 ppm to 600 ppm, based on total weight of the aqueous treatment composition.

[0067] The aqueous treatment composition may comprise less than 30% by weight nitric acid, such as less than 25% by weight, such as less than 20% by weight, such as less than 15% by weight, such as less than 10% by weight, such as less than 5% by weight, such as less than 1% by weight, based on the total weight of the composition.

[0068] The aqueous treatment composition may be substantially free, essentially free, or completely free of nitric acid.

[0069] The aqueous treatment composition may have a pH of no more than 7, such as no more than 6, such as no more than 5.5, such as no more than 5, such as no more than 4.5, such as no more than 4, such as no more than 3.5, such as no more than 3, and may have a pH of at least 1, such as at least 1.5, such as at least 2, such as at least 2.5. The aqueous treatment composition may have a pH of 1 to 7, such as 1 to 6, such as 1 to 5, such as 1 to 4.5, such as 1 to 4, such as 1 to 3.5, such as 1 to 3, such as 1.5 to 7, such as 1.5 to 6, such as 1.5 to 5, such as 1.5 to 4.5, such as 1.5 to 4, such as 1.5 to 3.5, such as 1.5 to 3, such as 2 to 7, such as 2 to 6, such as 2 to 5, such as 2 to 4.5, such as 2 to 4, such as 2 to 3.5, such as 2 to 3, such as 2.5 to 7, such as 2.5 to 6, such as 2.5 to 5, such as 2.5 to 4, such as 2.5 to 3.5, such as 2.5 to 3. The pH recited herein may be measured using a pH meter (interface, DualStar pH / ISE Dual Channel Benchtop Meter, available from ThermoFisher Scientific, Waitham, MA, USA) and pH probe (Fisher Scientific ACCUMET pH probe (Ag / AgCl reference electrode)) at ambient conditions. The pH of the aqueous treatment composition may be adjusted using, for example, any acid and / or base as is necessary. The pH of the aqueous treatment composition may be maintained through the inclusion of an acidic material, including water soluble and / or water dispersible acids, such as nitric acid, sulfuric acid, and / or phosphonic acid. The pH of the aqueous treatment composition may be maintained through the inclusion of a basic material, including water soluble and / or water dispersible bases, such as sodium hydroxide, sodium carbonate, potassium hydroxide, ammonium hydroxide, ammonia, and / or amines such as triethylamine, methylethyl amine, or mixtures thereof.

[0070] The aqueous treatment composition may exclude chromium or chromium- containing compounds. That is, the aqueous treatment composition may be substantially free,may be essentially free, and / or may be completely free of such chromium or chromium- containing compounds. As used herein, the term “chromium-containing compound” refers to materials that include trivalent and / or hexavalent chromium. Non-limiting examples of such materials include chromic acid, chromium trioxide, chromic acid anhydride, dichromate salts, such as ammonium dichromate, sodium dichromate, potassium dichromate, and calcium, barium, magnesium, zinc, cadmium, strontium dichromate, chromium (III) sulfate, chromium (III) chloride, and chromium (III) nitrate. When an aqueous treatment composition or a material deposited onto a substrate surface by deposition of the aqueous treatment composition is substantially free, essentially free, or completely free of chromium, this includes chromium in any form, such as, but not limited to, the trivalent and hexavalent chromium-containing compounds listed above.

[0071] The aqueous treatment composition comprises a carrier, often an aqueous medium, so that the aqueous treatment composition is in the form of a solution or dispersion. For example, the aqueous treatment composition comprises an aqueous composition.

[0072] The aqueous treatment composition may optionally contain other materials in addition to those described above, such as nonionic surfactants and auxiliaries conventionally used in the art of surface treatment of metals. In the aqueous medium, water dispersible organic solvents, for example, alcohols with up to above 8 carbon atoms, such as methanol, isopropanol, 1-methoxy-2-propanol, and the like, may be present; or glycol ethers such as the monoalkyl ethers of ethylene glycol, diethylene glycol, or propylene glycol, and the like; dimethylformamide; xylene; a base such as an amine, such as diisopropanolamine, triethylamine, dimethylethanolamine, and 2-amino-2-methylpropanol; and combinations thereof. When present, water dispersible organic solvents are typically used in amounts up to ten percent by volume, based on the total volume of the aqueous treatment composition. Other optional materials include surfactants that function as defoamers or substrate wetting agents. Anionic, cationic, amphoteric, and / or nonionic surfactants may be used.

[0073] The present disclosure also is directed to a method of treating a substrate comprising contacting at least a portion of the substrate with any of the aqueous treatment compositions of the present disclosure.

[0074] The aqueous treatment composition may be brought into contact with the metal substrate by any of a variety of known techniques, such as dipping or immersion, spraying,intermittent spraying, dipping followed by spraying, spraying followed by dipping, brushing, or roll-coating. The aqueous treatment composition may be in contact with at least a portion of the substrate surface for at least 5 seconds, such as at least 45 seconds, such as at least 60 seconds, such as at least 120 seconds, such as at least 180 seconds, such as no more than 5 minutes, such as no more than 4 minutes, such as no more than 3 minutes. The contacting may be for 5 seconds to 5 minutes, such as 30 seconds to 5 minutes, such as 30 seconds to 4 minutes, such as 30 seconds to 3 minutes. The aqueous treatment composition may be maintained (during contacting) at ambient temperature or higher, such as at least 21ºC (70ºF), such as at least 24ºC (75ºF), such as at least 26ºC (80ºF), such as at least 32ºC (90ºF), such as at least 37ºC (100ºF), such as at least 43ºC (110ºF), such as at least 48ºC (120ºF), such as 21ºC to 49ºC.

[0075] Following the contacting with the aqueous treatment composition, the substrate optionally may be air dried at room temperature or may be dried with hot air, for example, by using an air knife, by flashing off the water, by brief exposure of the substrate to a high temperature, such as by drying the substrate in an oven at 40ºC to 200ºC or in a heater assembly using, for example, infrared heat, such as for 10 minutes at 70ºC, or by passing the substrate between squeegee rolls.

[0076] At least a portion of the substrate surface may be cleaned prior to contacting at least a portion of the substrate surface with one of the aqueous treatment compositions described herein above to remove grease, dirt, and / or other extraneous matter. At least a portion of the surface of the substrate may be cleaned by physical and / or chemical means, such as mechanically abrading the surface and / or cleaning / degreasing the surface with commercially available alkaline cleaning agents that are well known to those skilled in the art. Such cleaners are often preceded and / or followed by a water rinse, such as with tap water, distilled water, or combinations thereof.

[0077] Following the cleaning step(s), the substrate optionally may be rinsed with tap water, deionized water, and / or an aqueous solution of rinsing agents to remove any residue. The wet substrate surface may be treated with one of the aqueous treatment compositions described above or the substrate may be dried prior to treating the substrate surface, such as air dried, for example, by using an air knife, by flashing off the water, by brief exposure of the substrate to a high temperature, such as 40ºC to 100ºC, such as 45ºC to 90ºC, or in a heater assembly using, forexample, infrared heat, such as for 10 minutes at 70ºC, or by passing the substrate between squeegee rolls.

[0078] The present disclosure is also directed to a pretreatment composition comprising an acid; a source of a metal comprising vanadium, manganese, nickel, silicon, ruthenium, rhodium, palladium, gold, tin, tantalum, tungsten, iridium, silver, mercury, thallium, lead, bismuth, polonium, platinum, niobium, titanium, cerium, or a combination thereof; a source of free fluoride; and an aqueous medium.

[0079] As used herein, “pretreatment composition” refers to a composition that is capable of reacting with and chemically altering the substrate surface and binding to it to form a film that affords corrosion protection. Although referred to as a pretreatment, the pretreatment composition may be the last treatment applied to the substrate, and / or the film formed from treatment with the pretreatment composition may be the outermost layer of the substrate.

[0080] As used herein, “pretreatment bath” refers to an aqueous bath containing the pretreatment composition and that may contain components that are byproducts of the process.

[0081] The substrate treated with the pretreatment composition disclosed herein may possess corrosion resistance (< 10 mΩ cm2 / h after electrochemical or thermal oxidation) as well as good electrical conductivity and low resistivity (< 10 mΩ cm2).

[0082] The acid may comprise a fluorometallic acid, including any described above with respect to the treatment composition.

[0083] The fluorometallic acid may be present in the pretreatment composition in an amount of at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight, such as at least 4% by weight, such as at least 5% by weight, such as at least 10% by weight, such as at least 15% by weight, such as at least 20% by weight, such as at least 25% by weight, based on the total weight of the pretreatment composition. The fluorometallic acid may be present in the pretreatment composition in an amount up to 28% by weight, such as up to 25% by weight, such as up to 20% by weight, such as up to 15% by weight, such as up to 10% by weight, such as up to 7% by weight, such as up to 5% by weight, based on the total weight of the pretreatment composition. The fluorometallic acid may be present in the pretreatment composition an amount of 0.5% to 28% by weight, such as 0.5% to 25% by weight, such as 0.5% to 20% by weight, such as 0.5% to 15% by weight, such as 0.5% to 10% by weight, such as 0.5% to 7% by weight, such as 0.5% to 5% by weight, such as 1% to 28% by weight,such as 1% to 25% by weight, such as 1% to 20% by weight, such as 1% to 15% by weight, such as 1% to 10% by weight, such as 1% to 7% by weight, such as 1% to 5% by weight, such as 2% to 28% by weight, such as 2% to 25% by weight, such as 2% to 20% by weight, such as 2% to 15% by weight, such as 2% to 10% by weight, such as 2% to 7% by weight, such as 2% to 5% by weight, such as 3% to 28% by weight, such as 3% to 25% by weight, such as 3% to 20% by weight, such as 3% to 15% by weight, such as 3% to 10% by weight, such as 3% to 7% by weight, such as 3% to 5% by weight, such as 4% to 28% by weight, such as 4% to 25% by weight, such as 4% to 20% by weight, such as 4% to 15% by weight, such as 4% to 10% by weight, such as 4% to 7% by weight, such as 4% to 5% by weight, such as 5% to 28% by weight, such as 5% to 25% by weight, such as 5% to 20% by weight, such as 5% to 15% by weight, such as 5% to 10% by weight, such as 5% to 7% by weight, such as 10% to 28% by weight, such as 10% to 25% by weight, such as 10% to 20% by weight, such as 10% to 15% by weight, such as 15% to 28% by weight, such as 15% to 25% by weight, such as 15% to 20% by weight, such as 20% to 28% by weight, such as 20% to 25% by weight, such as 25% to 28% by weight, based on the total weight of the pretreatment composition.

[0084] The source of free fluoride may comprise a fluoride salt. Non-limiting examples of the fluoride salt include ammonium and alkali metal fluorides, such as ammonium bifluoride, potassium fluoride, sodium fluoride, and the like.

[0085] The fluoride salt may be present in an amount of at least 0.1% by weight, based on the total weight of the pretreatment composition, such as at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight. The fluoride salt may be present in an amount up to the solubility limit of the fluoride salt, such as no more than 38% by weight, based on the total weight of the pretreatment composition, such as no more than 20% by weight, such as no more than 15% by weight, such as no more than 10% by weight, such as no more than 7% by weight, such as no more than 5% by weight, such as no more than 4% by weight, such as no more than 3.5% by weight. The fluoride salt may be present in an amount of 0.1% to 38% by weight, such as 0.1% to 20% by weight, based on the total weight of the pretreatment composition, such as 0.1% to 15% by weight, such as 0.1% to 10% by weight, such as 0.1% to 7% by weight, such as 0.1% to 5% by weight, such as 0.1% to 4% by weight, such as 0.1% to 3.5% by weight, such as 0.5% to 38% by weight, such as 0.5% to 20% by weight, such as 0.5% to 15% by weight, such as 0.5% to 10% by weight, such as 0.5% to 7% byweight, such as 0.5% to 5% by weight, such as 0.5% to 4% by weight, such as 0.5% to 3.5% by weight, such as 1% to 38% by weight, such as 1% to 20% by weight, such as 1% to 15% by weight, such as 1% to 10% by weight, such as 1% to 7% by weight, such as 1% to 5% by weight, such as 1% to 4% by weight, such as 1% to 3.5% by weight, such as 2% to 38% by weight, such as 2% to 20% by weight, such as 2% to 15% by weight, such as 2% to 10% by weight, such as 2% to 7% by weight, such as 2% to 5% by weight, such as 2% to 4% by weight, such as 2% to 3.5% by weight, such as 3% to 38% by weight, such as 3% to 20% by weight, such as 3% to 15% by weight, such as 3% to 10% by weight, such as 3% to 7% by weight, such as 3% to 5% by weight, such as 3% to 4% by weight, such as 3% to 3.5% by weight.

[0086] The free fluoride may be present in the pretreatment composition in an amount of at least 2 ppm, such as at least 10 ppm, such as at least 25 ppm, such as at least 35 ppm, such as at least 100 ppm, such as at least 200 ppm, based on total weight of the pretreatment composition. The free fluoride may be present in the pretreatment composition in an amount of no more than 230,000 ppm, such as no more than 100,000 ppm, such as no more than 50,000 ppm, such as no more than 5,000 ppm, such as no more than 2,500 ppm, such as no more than 2,000 ppm, such as no more than 1,500 ppm, such as no more than 1,000 ppm, such as no more than 600 ppm, such as no more than 200 ppm, such as no more than 100 ppm, such as no more than 75 ppm, based on total weight of the pretreatment composition. The free fluoride may be present in the pretreatment composition in an amount of 2 ppm to 230,000 ppm, such as 2 ppm to 100,000 ppm, such as 2 ppm to 50,000 ppm, such as 2 ppm to 5,000 ppm, such as 2 ppm to 2,500 ppm, such as 2 ppm to 2,000 ppm, such as 2 ppm to 1,500 ppm, such as 2 ppm to 1,000 ppm, such as 2 ppm to 600 ppm, such as 2 ppm to 200 ppm, such as 2 ppm to 100 ppm, such as 2 ppm to 75 ppm, such as 10 ppm to 230,000 ppm, such as 10 ppm to 100,000 ppm, such as 10 ppm to 50,000 ppm, such as 10 ppm to 5,000 ppm, such as 10 ppm to 2,500 ppm, such as 10 ppm to 2,000 ppm, such as 10 ppm to 1,500 ppm, such as 10 ppm to 1,000 ppm, such as 10 ppm to 600 ppm, such as 10 ppm to 200 ppm, such as 10 ppm to 100 ppm, such as 10 ppm to 75 ppm, such as 25 ppm to 100,000 ppm, such as 25 ppm to 50,000 ppm, such as 25 ppm to 5,000 ppm, such as 25 ppm to 2,500 ppm, such as 25 ppm to 2,000 ppm, such as 25 ppm to 1,500 ppm, such as 25 ppm to 1,000 ppm, such as 25 ppm to 600 ppm, such as 25 ppm to 100 ppm, such as 25 ppm to 75 ppm, such as 35 ppm to 100,000 ppm, such as 35 ppm to 50,000 ppm, such as 35 ppm to 5,000 ppm, such as 35 ppm to 2,500 ppm, such as 35 ppm to 2,000 ppm, such as 35 ppm to 1,500ppm, such as 35 ppm to 1,000 ppm, such as 35 ppm to 600 ppm, such as 35 ppm to 200 ppm, such as 35 ppm to 100 ppm, such as 35 ppm to 75 ppm, such as 100 ppm to 100,000 ppm, such as 100 ppm to 50,000 ppm, such as 100 ppm to 5,000 ppm, such as 100 ppm to 2,500 ppm, such as 100 ppm to 2,000 ppm, such as 100 ppm to 1,500 ppm, such as 100 ppm to 1,000 ppm, such as 100 ppm to 200 ppm, such as 200 ppm to 100,000 ppm, such as 200 ppm to 50,000 ppm, such as 200 ppm to 5,000 ppm, such as 200 ppm to 2,500 ppm, such as 200 ppm to 2,000 ppm, such as 200 ppm to 1,500 ppm, such as 200 ppm to 1,000 ppm, such as 200 ppm to 600 ppm, based on total weight of the pretreatment composition.

[0087] The pretreatment composition may comprise total fluoride in an amount of at least 50 ppm, such as at least 75 ppm, such as at least 100 ppm, based on total weight of the pretreatment composition. The pretreatment composition may comprise total fluoride in an amount of no more than 230,000 ppm, such as no more than 100,000 ppm, such as no more than 50,000 ppm, such as no more than 5,000 ppm, such as no more than 3,000 ppm, such as no more than 2,500 ppm, based on total weight of the pretreatment composition. The pretreatment composition may comprise total fluoride in an amount of 50 ppm to 230,000 ppm, such as 50 ppm to 100,000 ppm, such as 50 ppm to 50,000 ppm, such as 50 ppm to 5,000 ppm, such as 75 ppm to 230,000 ppm, such as 75 ppm to 100,000 ppm, such as 75 ppm to 50,000 ppm, such as 75 ppm to 3,000 ppm, such as 100 ppm to 230,000 ppm, such as 100 ppm to 100,000 ppm, such as 100 ppm to 50,000 ppm, such as 100 ppm to 2,500 ppm, based on total weight of the pretreatment composition. The total fluoride may be calculated by comparing the weight of the fluoride supplied in the pretreatment composition with the total weight of the pretreatment composition.

[0088] The pretreatment composition further comprises a source of a metal comprising vanadium, manganese, nickel, silicon, ruthenium, rhodium, palladium, gold, tin, tantalum, tungsten, iridium, silver, mercury, thallium, lead, bismuth, polonium, platinum, niobium, titanium, cerium, or a combination thereof. Use of the source of the metal results in the at least a portion of the metal being present in the pretreatment composition in a solubilized form.

[0089] The metal may comprise, consist essentially of, or consist of niobium.

[0090] The source of the metal may comprise, consist essentially of, or consist of soluble forms of niobium compounds including, for example, ammonium niobium oxalate, niobium oxide, and niobium oxide hydrate.

[0091] The source of the metal may comprise, consist essentially of, or consist of soluble forms of platinum compounds including, for example, chloroplatinic acid (also known as hexachloroplatinic acid or hydrogen hexachloroplatinate(IV), with the formula [H3O]2[PtCl6](H2O)x(0 ≤ x ≤ 6) or shorthand formula H2PtCl6), potassium hexachloroplatinate (with the formula K2PtCl6), ammonium hexachloroplatinate(IV) (with the formula (NH4)2PtCl6), potassium tetrachloroplatinate(II) (with the formula K2PtCl4), ammonium tetrachloroplatinate(II) (with the formula (NH4)2PtCl4), platinum (IV) chloride (with the formula PtCl4), and platinum (II) chloride (with the formula PtCl2), tetraamineplatinum(II)nitrate (with the formula (NH3)4Pt (NO3)2), platinum (IV) nitrate (with the formula Pt(NO3)4), and platinum (II) sulfate (with the formula PtSO4).

[0092] As used herein, a “soluble” metal refers to metal in a form that is capable of being dissolved in the aqueous medium. As used herein, a “solubilized” metal refers to metal dissolved in the aqueous medium.

[0093] The source of the metal is present in an amount such that solubilized metal is present in an amount of at least 100 ppm, such as at least 500 ppm, such as at least 1,000 ppm, such as at least 1,500 ppm, such as at least 2,000 ppm, such as at least 2,500 ppm, such as at least 3,000 ppm, such as at least 3,500 ppm, such as at least 4,000 ppm, such as at least 4,500 ppm, such as at least 5,000 ppm, such as at least 5,500 ppm, such as at least 6,000 ppm, such as at least 6,500 ppm, such as at least 7,000 ppm, such as at least 7,500 ppm, such as at least 8,000 ppm, such as at least 8,500 ppm, such as at least 9,000 ppm, such as at least 9,500 ppm, such as at least 10,000 ppm, such as at least 10,500 ppm. The source of the metal is present in an amount such that solubilized metal is present in an amount of no more than 13,000 ppm, such as no more than 11,000 ppm, such as no more than 10,000 ppm, such as no more than 9,000 ppm, such as no more than 8,000 ppm, such as no more than 7,000 ppm, such as no more than 6,000 ppm, such as no more than 5,000 ppm, such as no more than 4,000 ppm, such as no more than 3,000 ppm, such as no more than 2,000 ppm, such as no more than 1,000 ppm. The source of the metal is present in an amount such that solubilized metal is present in an amount of 100 ppm to 13,000 ppm, such as 100 ppm to 11,000 ppm, such as 100 ppm to 9,000 ppm, such as 100 ppm to 8,000 ppm, such as 100 ppm to 7,000 ppm, such as 100 ppm to 6,000 ppm, such as 100 ppm to 5,000 ppm, such as 100 ppm to 4,000 ppm, such as 100 ppm to 3,000 ppm, such as 100 ppm to 2,000 ppm, such as 100 ppm to 1,000 ppm, such as 500 ppm to 13,000 ppm, such as 500 ppm to 11,000ppm, such as 500 ppm to 9,000 ppm, such as 500 ppm to 8,000 ppm, such as 500 ppm to 7,000 ppm, such as 500 ppm to 6,000 ppm, such as 500 ppm to 5,000 ppm, such as 500 ppm to 4,000 ppm, such as 500 ppm to 3,000 ppm, such as 500 ppm to 2,000 ppm, such as 500 ppm to 1,000 ppm, such as 1,000 ppm to 13,000 ppm, such as 1,000 ppm to 11,000 ppm, such as 1,000 ppm to 9,000 ppm, such as 1,000 ppm to 8,000 ppm, such as 1,000 ppm to 7,000 ppm, such as 1,000 ppm to 6,000 ppm, such as 1,000 ppm to 5,000 ppm, such as 1,000 ppm to 4,000 ppm, such as 1,000 ppm to 3,000 ppm, such as 1,000 ppm to 2,000 ppm, such as 1,500 ppm to 13,000 ppm, such as 1,500 ppm to 11,000 ppm, such as 1,500 ppm to 9,000 ppm, such as 1,500 ppm to 8,000 ppm, such as 1,500 ppm to 7,000 ppm, such as 1,500 ppm to 6,000 ppm, such as 1,500 ppm to 5,000 ppm, such as 1,500 ppm to 4,000 ppm, such as 1,500 ppm to 3,000 ppm, such as 1,500 ppm to 2,000 ppm, such as 2,000 ppm to 13,000 ppm, such as 2,000 ppm to 11,000 ppm, such as 2,000 ppm to 9,000 ppm, such as 2,000 ppm to 8,000 ppm, such as 2,000 ppm to 7,000 ppm, such as 2,000 ppm to 6,000 ppm, such as 2,000 ppm to 5,000 ppm, such as 2,000 ppm to 4,000 ppm, such as 2,000 ppm to 3,000 ppm, such as 2,500 ppm to 13,000 ppm, such as 2,500 ppm to 11,000 ppm, such as 2,500 ppm to 9,000 ppm, such as 2,500 ppm to 8,000 ppm, such as 2,500 ppm to 7,000 ppm, such as 2,500 ppm to 6,000 ppm, such as 2,500 ppm to 5,000 ppm, such as 2,500 ppm to 4,000 ppm, such as 2,500 ppm to 3,000 ppm, such as 3,000 ppm to 13,000 ppm, such as 3,000 ppm to 11,000 ppm, such as 3,000 ppm to 9,000 ppm, such as 3,000 ppm to 8,000 ppm, such as 3,000 ppm to 7,000 ppm, such as 3,000 ppm to 6,000 ppm, such as 3,000 ppm to 5,000 ppm, such as 3,000 ppm to 4,000 ppm, such as 3,500 ppm to 13,000 ppm, such as 3,500 ppm to 11,000 ppm, such as 3,500 ppm to 9,000 ppm, such as 3,500 ppm to 8,000 ppm, such as 3,500 ppm to 7,000 ppm, such as 3,500 ppm to 6,000 ppm, such as 3,500 ppm to 5,000 ppm, such as 3,500 ppm to 4,000 ppm, such as 4,000 ppm to 13,000 ppm, such as 4,000 ppm to 11,000 ppm, such as 4,000 ppm to 10,000 ppm, such as 4,000 ppm to 9,000 ppm, such as 4,000 ppm to 8,000 ppm, such as 4,000 ppm to 7,000 ppm, such as 4,000 ppm to 6,000 ppm, such as 4,000 ppm to 5,000 ppm, such as 4,500 ppm to 13,000 ppm, such as 4,500 ppm to 11,000 ppm, such as 4,500 ppm to 10,000 ppm, such as 4,500 ppm to 9,000 ppm, such as 4,500 ppm to 8,000 ppm, such as 4,500 ppm to 7,000 ppm, such as 4,500 ppm to 6,000 ppm, such as 4,500 ppm to 5,000 ppm, such as 5,000 ppm to 13,000 ppm, such as 5,000 ppm to 11,000 ppm, such as 5,000 ppm to 10,000 ppm, such as 5,000 ppm to 9,000 ppm, such as 5,000 ppm to 8,000 ppm, such as 5,000 ppm to 7,000 ppm, such as 5,000 ppm to 6,000 ppm, such as 5,500 ppm to 13,000 ppm, such as5,500 ppm to 11,000 ppm, such as 5,500 ppm to 10,000 ppm, such as 5,500 ppm to 9,000 ppm, such as 5,500 ppm to 8,000 ppm, such as 5,500 ppm to 7,000 ppm, such as 5,500 ppm to 6,000 ppm, such as 6,000 ppm to 13,000 ppm, such as 6,000 ppm to 11,000 ppm, such as 6,000 ppm to 10,000 ppm, such as 6,000 ppm to 9,000 ppm, such as 6,000 ppm to 8,000 ppm, such as 6,000 ppm to 7,000 ppm, such as 6,500 ppm to 13,000 ppm, such as 6,500 ppm to 11,000 ppm, such as 6,500 ppm to 10,000 ppm, such as 6,500 ppm to 9,000 ppm, such as 6,500 ppm to 8,000 ppm, such as 6,500 ppm to 7,000 ppm, such as 7,000 ppm to 13,000 ppm, such as 7,000 ppm to 11,000 ppm, such as 7,000 ppm to 10,000 ppm, such as 7,000 ppm to 9,000 ppm, such as 7,000 ppm to 8,000 ppm, such as 7,500 ppm to 13,000 ppm, such as 7,500 ppm to 11,000 ppm, such as 7,500 ppm to 10,000 ppm, such as 7,500 ppm to 9,000 ppm, such as 7,500 ppm to 8,000 ppm, such as 8,000 ppm to 13,000 ppm, such as 8,000 ppm to 11,000 ppm, such as 8,000 ppm to 10,000 ppm, such as 8,000 ppm to 9,000 ppm, such as 8,500 ppm to 13,000 ppm, such as 8,500 ppm to 11,000 ppm, such as 8,500 ppm to 10,000 ppm, such as 8,500 ppm to 9,000 ppm, such as 9,000 ppm to 13,000 ppm, such as 9,000 ppm to 11,000 ppm, such as 9,000 ppm to 10,000 ppm, such as 9,500 ppm to 13,000 ppm, such as 9,500 ppm to 11,000 ppm, such as 10,000 ppm to 13,000 ppm, such as 10,000 ppm to 11,000 ppm, such as 10,500 ppm to 13,000 ppm, such as 10,500 ppm to 11,000 ppm.

[0094] The method of the present disclosure optionally may further comprise contacting at least a portion of the metal substrate with the pretreatment composition. Contacting at least a portion of the metal substrate with the pretreatment composition may be done after treatment of the substrate with the treatment composition. The method of contacting, conditions, and contact time may be the same as for the aqueous treatment composition. Optionally, the pretreatment composition may be heated and / or stirred during the contacting of the metal substrate with the pretreatment composition. The temperature of the heated pretreatment composition may be 30°C to 60°C, such as 30°C to 50°C, such as 35°C to 45°C, and the stirring speed may be any appropriate speed, such as 100 to 500 rpm, such as 150 to 400 rpm, such as 200 to 300 rpm.

[0095] The present disclosure is also directed to a kit comprising one of the aqueous treatment compositions disclosed herein and / or one of the pretreatment compositions disclosed herein, and optionally instructions for treating a substrate with the aqueous treatment composition, the pretreatment composition, or both the aqueous treatment composition and the pretreatment composition.

[0096] The present disclosure also is directed to a metal substrate comprising at least a portion of its surface treated with one of the aqueous treatment compositions disclosed herein. The metal substrate may also be treated with one of the pretreatment compositions disclosed herein.

[0097] The present disclosure also is directed to a metal substrate comprising at least a portion of its surface treated with one of the pretreatment compositions disclosed herein.

[0098] The present disclosure also is directed to a metal substrate treated according to the method of treating a substrate disclosed herein.

[0099] Suitable substrates that may be used include metal substrates, metal alloy substrates, and / or substrates that have been metallized, such as nickel-plated plastic. The metal or metal alloy can comprise or be steel, stainless steel, aluminum, zinc, nickel, and / or magnesium. For example, the steel substrate could be cold rolled steel, hot rolled steel, electrogalvanized steel, and / or hot dipped galvanized steel. Aluminum alloys of the 1XXX, 2XXX, 3XXX, 4XXX, 5XXX, 6XXX, or 7XXX series, as well as clad aluminum alloys, also may be used as the substrate. Aluminum alloys may comprise, for example, 0.01% by weight copper to 10% by weight copper, based on the total weight of the alloy. Aluminum alloys which are treated may also include castings, such as IXX.X, 2XX.X, 3XX.X, 4XX.X, 5XX.X, 6XX.X, 7XX.X, 8XX.X, or 9XX.X (e.g., A356.0). Magnesium alloys of the AZXX (including Eform Plus), AMXX, EVXX, ZKXX, ZEXX, ZCXX, HKXX, HZXX, QEXX, QHXX, WEXX, ZEK100, or Elektron 21 series also may be used as the substrate. The substrate used may also comprise titanium and / or titanium alloys, zinc and / or zinc alloys, and / or nickel and / or nickel alloys. Suitable substrates for use include those that are often used in the assembly of a vehicle, such as vehicular bodies (e.g., without limitation, door, body panel, trunk deck lid, roof panel, hood, roof and / or stringers, rivets, landing gear components, and / or skins used on an aircraft), a vehicular frame, vehicular parts, motorcycles, wheels, industrial structures and components such as appliances, including washers, dryers, refrigerators, stoves, dishwashers, and the like, personal electronics, agricultural equipment, lawn and garden equipment, air conditioning units, heat pump units, heat exchangers, lawn furniture, and other articles. As used herein, “vehicle” or variations thereof includes, but is not limited to, aircraft, including civilian, commercial and military aircraft, and / or land vehicles such as automobiles, motorcycles, trucks, tanks, and / or armored cars. Suitable substrate also includes aircraft and aircrafts parts, windmills andwindmill components, marine vessels and marine vessel components, and the like. The metal substrate also may be in the form of, for example, a sheet of metal or a fabricated part.

[0100] A suitable substrate for use includes an article. In examples, the substrate may be a multi-metal article. As used herein, the term “multi-metal article” refers to (1) an article that has at least one surface comprised of a first metal and at least one surface comprised of a second metal that is different from the first metal, (2) a first article that has at least one surface comprised of a first metal and a second article that has at least one surface comprised of a second metal that is different from the first metal, or (3) both (1) and (2).

[0101] In examples, the substrate may comprise a three-dimensional component formed by an additive manufacturing process such as selective laser melting, e-beam melting, directed energy deposition, binder jetting, metal extrusion, diffusion bonding, welding and the like. In examples, the three-dimensional component may be a metal and / or resinous component.

[0102] The treated metal substrate may have a ratio of the percentage of Ti3+to the percentage of Ti2+of the treated metal substrate as measured using high resolution X-ray photoelectron spectroscopy of at least 0.7, such as at least 0.9, such as at least 1, such as at least 1.2, such as at least 1.4, such as at least 1.6, such as at least 1.8, such as at least 2, such as at least 2.1, such as at least 2.2. High resolution X-ray photoelectron spectroscopy may be performed as described in the examples.

[0103] The total percentage of titanium present on the surface of the metal substrate treated with the aqueous treatment composition as measured using high resolution X-ray photoelectron spectroscopy may be at least 2% greater than the total percentage of titanium present on the surface of the metal substrate prior to treatment, such as at least 4% greater, such as at least 6% greater, such as at least 8% greater. High resolution X-ray photoelectron spectroscopy may be performed as described in the examples.

[0104] The percentage of Ti3+present on the surface of the metal substrate treated with the aqueous treatment composition as measured using high resolution X-ray photoelectron spectroscopy may be at least 1% greater than the percentage of Ti3+present on the surface of the metal substrate prior to treatment, such as at least 2% greater, such as at least 3% greater, such as at least 4% greater. High resolution X-ray photoelectron spectroscopy may be performed as described in the examples.

[0105] The percentage of Ti2+present on the surface of the metal substrate treated with the aqueous treatment composition as measured using high resolution X-ray photoelectron spectroscopy may be at least 2% less than the percentage of Ti2+present on the surface of the metal substrate prior to treatment, such as at least 4% less, such as at least 6% less, such as at least 8% less. High resolution X-ray photoelectron spectroscopy may be performed as described in the examples.

[0106] The surface crystallinity of measured using grazing incidence X-ray diffraction to determine the (101):(002) reflection ratio of the surface of the metal substrate treated with the aqueous treatment composition may be at least 5% less than the surface of the metal substrate prior to treatment, such as at least 10% less, such as at least 15% less, such as at least 20% less. The surface crystallinity may be measured using grazing incidence X-ray diffraction to determine the (101):(002) reflection ratio as described in the examples.

[0107] The roughness of the surface of the metal substrate treated with the aqueous treatment composition as measured using confocal laser scanning microscopy (CLSM) may be at least 1.3 times rougher than the surface prior to treatment, such as at least 1.5 times rougher, such as at least 1.8 times rougher, such as at least 2 times rougher, such as at least 2.2 times rougher, such as at least 2.4 times rougher, such as at least 2.6 times rougher. The roughness of the surface may be measured by the SURFACE ROUGHNESS TEST METHOD described in the examples section.

[0108] The treated metal substrate may have an interfacial contact resistivity of less than 5 mΩ cm2, such as less than 3 mΩ cm2, such as less than 1 mΩ cm2, as measured according to the ICR TEST METHOD.

[0109] The treated metal substrate may have an interfacial contact resistivity of less than 20 mΩ cm2after 100 hours of electrochemical oxidation exposure, such as less than 15 mΩ cm2, such as less than 10 mΩ cm2, such as less than 5 mΩ cm2, such as less than 3 mΩ cm2, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0110] The treated metal substrate may have an interfacial contact resistivity of less than 40 mΩ cm2after 250 hours of electrochemical oxidation exposure, such as less than 35 mΩ cm2, such as less than 30 mΩ cm2, such as less than 25 mΩ cm2, such as less than 20 mΩ cm2, such as less than 15 mΩ cm2, such as less than 10 mΩ cm2, such as less than 5 mΩ cm2, such as less than3 mΩ cm2, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0111] The treated metal substrate may have an interfacial contact resistivity of less than 40 mΩ cm2after exposure of the substate to thermal oxidation testing, such as less than 35 mΩ cm2, such as less than 30 mΩ cm2, such as less than 25 mΩ cm2, such as less than 20 mΩ cm2, such as less than 15 mΩ cm2, such as less than 10 mΩ cm2, such as less than 5 mΩ cm2, such as less than 3 mΩ cm2, as measured according to the ICR THERMAL OXIDATION TEST METHOD.

[0112] The treated metal substrate may have a TOF-SIMs depth profile for H+ / Ti+relative ion intensity inverse peak within 0-5 nm depth of at least 0.002, such as at least 0.003, such as at least 0.004, as measured according to the TOF-SIMs TEST METHOD.

[0113] The treated metal substrate may have a TOF-SIMs depth profile for Na+ / Ti+relative ion intensity inverse peak within 0.5 nm depth of no more than 3.2, such as no more than 3, such as no more than 2.5, such as no more than 2, such as no more than 1.5, such as no more than 1, as measured according to the TOF-SIMs TEST METHOD.

[0114] The metal substrate treated with the aqueous treatment composition and pretreatment composition may have an interfacial contact resistivity growth of less than 10 mΩ cm2 / h after 50 hours of electrochemical oxidation exposure, such as less than 5 mΩ cm2 / h, such as less than 1 mΩ cm2 / h, such as less than 0.5 mΩ cm2 / h, such as less than 0.3 mΩ cm2 / h, such as less than 0.1 mΩ cm2 / h, such as less than 0.05 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0115] The metal substrate treated with the aqueous treatment composition and pretreatment composition may have an interfacial contact resistivity growth of less than 10 mΩ cm2 / h after 100 hours of electrochemical oxidation exposure, such as less than 5 mΩ cm2 / h, such as less than 1 mΩ cm2 / h, such as less than 0.5 mΩ cm2 / h, such as less than 0.3 mΩ cm2 / h, such as less than 0.1 mΩ cm2 / h, such as less than 0.05 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0116] The metal substrate treated with the aqueous treatment composition and pretreatment composition may have an interfacial contact resistivity growth of less than 10 mΩ cm2 / h after 250 hours of electrochemical oxidation exposure, such as less than 5 mΩ cm2 / h, such as less than 1 mΩ cm2 / h, such as less than 0.5 mΩ cm2 / h, such as less than 0.3 mΩ cm2 / h, suchas less than 0.1 mΩ cm2 / h, such as less than 0.05 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0117] According to the present disclosure, the metal substrate of the composite structure may comprise a porous metal substrate comprising a surface having a plurality of apertures.

[0118] The porous metal substrate may comprise a mesh, an expanded metal, a perforated metal, a woven metal, a grid, sintered particles, sintered felt, or a combination thereof.

[0119] As used herein, the term “expanded metal” refers to a metal sheet that has been slit and stretched to a wide array of typically diamond shaped openings.

[0120] The thickness of the porous metal substrate is not limited and may depend upon the intended end use of the composite structure. The porous metal substrate may have a thickness of at least 0.015 mm, such as at least 0.02 mm, such as at least 0.08 mm, such as at least 0.10 mm, such as at least 0.15 mm, such as at least 0.20 mm. The porous metal substrate may have a thickness of no more than 1 mm, such as no more than 0.70 mm, such as no more than 0.50 mm, such as no more than 0.30 mm, such as no more than 0.20 mm, such as no more than 0.15 mm, such as no more than 0.10 mm. The porous metal substrate may have a thickness of 0.015 to 1 mm, such as 0.015 to 0.70 mm, such as 0.015 to 0.50 mm, such as 0.015 to 0.30 mm, such as 0.015 to 0.20 mm, such as 0.015 to 0.15 mm, such as 0.015 to 0.10 mm, such as 0.02 to 1 mm, such as 0.02 to 0.70 mm, such as 0.02 to 0.50 mm, such as 0.02 to 0.30 mm, such as 0.02 to 0.20 mm, such as 0.02 to 0.15 mm, such as 0.02 to 0.10 mm, such as 0.08 to 1 mm, such as 0.08 to 0.70 mm, such as 0.08 to 0.50 mm, such as 0.08 to 0.30 mm, such as 0.08 to 0.20 mm, such as 0.08 to 0.15 mm, such as 0.08 to 0.10 mm, such as 0.10 to 1 mm, such as 0.10 to 0.70 mm, such as 0.10 to 0.50 mm, such as 0.10 to 0.30 mm, such as 0.10 to 0.20 mm, such as 0.10 to 0.15 mm, such as 0.15 to 1 mm, such as 0.15 to 0.70 mm, such as 0.15 to 0.50 mm, such as 0.15 to 0.30 mm, such as 0.15 to 0.20 mm, such as 0.20 to 1 mm, such as 0.20 to 0.70 mm, such as 0.20 to 0.50 mm, such as 0.20 to 0.30 mm.

[0121] The content and form of the apertures of the porous metal substrate may depend upon the intended end use of the substrate. For example, the apertures may be uniformly distributed over the entire surface of the porous metal substrate, or a portion of the surface of the porous metal substrate. Alternatively, the apertures may be non-uniformly distributed over the entire surface of the porous metal substrate, or non-uniformly distributed over the entire surface of the porous metal substrate. The apertures may comprise any regular or irregular shape, or anycombination thereof. For example, the porous metal substrate may comprise irregular, round, elliptical, triangular, square, rectangular, rhombus, parallelogram, or polygonal shaped apertures, as well as combinations thereof.

[0122] The number of apertures is not limited and may depend upon the end use of the metal substrate. The substrate may comprise at least 2 apertures / cm2of the substrate surface, such as at least 5, such as at least 9, such as at least 15, such as at least 20, such as at least 35, such as at least 60, such as at least 100, such as at least 150, such as at least 200. The substrate may comprise no more than 1,400 apertures / cm2of the substrate surface, such as no more than 550, such as no more than 250, such as no more than 175, such as no more than 120, such as no more than 80, such as no more than 60, such as no more than 40, such as no more than 30. The substrate may comprise 2 to 1,400 apertures / cm2of the substrate surface, such as 2 to 550, such as 2 to 250, such as 2 to 175, such as 2 to 120, such as 2 to 80, such as 2 to 60, such as 2 to 40, such as 2 to 30, such as 5 to 1,400, such as 5 to 550, such as 5 to 250, such as 5 to 175, such as 5 to 120, such as 5 to 80, such as 5 to 60, such as 5 to 40, such as 5 to 30, such as 9 to 1,400, such as 9 to 550, such as 9 to 250, such as 9 to 175, such as 9 to 120, such as 9 to 80, such as 9 to 60, such as 9 to 40, such as 9 to 30, such as 15 to 1,400, such as 15 to 550, such as 15 to 250, such as 15 to 175, such as 15 to 120, such as 15 to 80, such as 15 to 60, such as 15 to 40, such as 15 to 30, such as 20 to 1,400, such as 20 to 550, such as 20 to 250, such as 20 to 175, such as 20 to 120, such as 20 to 80, such as 20 to 60, such as 20 to 40, such as 20 to 30, such as 35 to 1,400, such as 35 to 550, such as 35 to 250, such as 35 to 175, such as 35 to 120, such as 35 to 80, such as 35 to 60, such as 35 to 40, such as 60 to 1,400, such as 60 to 550, such as 60 to 250, such as 60 to 175, such as 60 to 120, such as 60 to 80, such as 100 to 1,400, such as 100 to 550, such as 100 to 250, such as 100 to 175, such as 100 to 120, such as 150 to 1,400, such as 150 to 550, such as 150 to 250, such as 150 to 175, such as 200 to 1,400, such as 200 to 550, such as 200 to 250.

[0123] The percentage of the porous metal substrate surface area comprising an aperture is not limited and may depend upon the end use of the composite. The apertures may comprise at least 10% of the substrate surface area, such as at least 15%, such as at least 20%, such as at least 30%, such as at least 35%. The apertures may comprise no more than 90% of the substrate surface area, such as no more than 85%, such as no more than 80%. The apertures may comprise 10% to 90% of the substrate surface area, such as 10% to 85%, such as 10% to 80%, such as15% to 90%, such as 15% to 85%, such as 15% to 80%, such as 20% to 90%, such as 20% to 85%, such as 20% to 80%, such as 30% to 90%, such as 30% to 85%, such as 30% to 80%, such as 35% to 90%, such as 35% to 85%, such as 35% to 80%.

[0124] The size of the aperture may also be defined by other metrics depending upon the shape of the aperture. For example, a non-limited example of an expanded metal mesh porous metal substrate is shown in Figure 1. Figure 1 shows an aperture of an expanded metal mesh porous metal substrate. The porous metal substrate comprises strands of metal that meet at nodes to form a rhombus (i.e., diamond) shaped aperture. The size of the aperture may be described by referring to the distance between opposite nodes of the rhombus. For example, the shorter distance is denoted by the SWO and SWD notation on the right side of the figure. SWD stands for short way of the diamond and is the length of the short axis way of the diamond, measured from the center of the joint (i.e., node) to the center of the joint on the opposing side of the diamond. SWO stands for short way of the opening and is the length of the short axis way of the diamond, measured from the opposite vertices of the aperture. The longer distance is denoted by the LWO and LWD notation of the bottom of the figure. LWD stands for long way of the diamond and is the length of the long axis way of the diamond, measured from the center of the joint (i.e., node) to the center of the joint on the opposing side of the diamond. LWO stands for long way of the opening and is the length of the long axis way of the diamond, measured from the opposite vertices of the aperture.

[0125] The SWD and LWD, as well as the SWO and LWO, distances are not limiting and may depend upon the end use of the composite.

[0126] The porous metal substrate may comprise apertures having an SWD distance of at least 0.4 mm, such as at least 0.9 mm, such as at least 1.2 mm, such as at least 1.5 mm. The porous metal substrate may comprise apertures having an SWD distance of no more than 10 mm, such as no more than 4 mm, such as no more than 3.5 mm, such as no more than 2.9 mm, such as no more than 2.3 mm, such as no more than 1.8 mm. The porous metal substrate may comprise apertures having an SWD distance of 0.4 to 10 mm, such as 0.4 to 4 mm, such as 0.4 to 3.5 mm, such as 0.4 to 2.9 mm, such as 0.4 to 2.3 mm, such as 0.4 to 1.8 mm, such as 0.9 to 10 mm, such as 0.9 to 4 mm, such as 0.9 to 3.5 mm, such as 0.9 to 2.9 mm, such as 0.9 to 2.3 mm, such as 0.9 to 1.8 mm, such as 1.2 to 10 mm, such as 1.2 to 4 mm, such as 1.2 to 3.5 mm, such as 1.2 to 2.9mm, such as 1.2 to 2.3 mm, such as 1.2 to 1.8 mm, such as 1.5 to 10 mm, such as 1.5 to 4 mm, such as 1.5 to 3.5 mm, such as 1.5 to 2.9 mm, such as 1.5 to 2.3 mm, such as 1.5 to 1.8 mm.

[0127] The porous metal substrate may comprise apertures having an LWD distance of at least 0.5 mm, such as at least 0.7 mm, such as at least 1.5 mm, such as at least 2 mm, such as at least 2.5 mm, such as at least 3 mm. The porous metal substrate may comprise apertures having an LWD distance of no more than 13 mm, such as no more than 7.5 mm, such as no more than 5 mm, such as no more than 3.5 mm, such as no more than 3.2 mm, such as no more than 2.5 mm. The porous metal substrate may comprise apertures having an LWD distance of 0.5 mm to 13 mm, such as 0.5 to 7.5 mm, such as 0.5 to 5 mm, such as 0.5 to 3.5 mm, such as 0.5 to 3.2 mm, such as 0.5 to 2.5 mm, such as 0.7 mm to 13 mm, such as 0.7 to 7.5 mm, such as 0.7 to 5 mm, such as 0.7 to 3.5 mm, such as 0.7 to 3.2 mm, such as 0.7 to 2.5 mm, such as 1.5 to 13 mm, such as 1.5 to 7.5 mm, such as 1.5 to 5 mm, such as 1.5 to 3.5 mm, such as 1.5 to 3.2 mm, such as 1.5 to 2.5 mm, such as 2 to 13 mm, such as 2 to 7.5 mm, such as 2 to 5 mm, such as 2 to 3.5 mm, such as 2 to 3.2 mm, such as 2 to 2.5 mm, such as 2.5 to 13 mm, such as 2.5 to 7.5 mm, such as 2.5 to 5 mm, such as 2.5 to 3.5 mm, such as 2.5 to 3.2 mm, such as 3 to 13 mm, such as 3 to 7.5 mm, such as 3 to 5 mm, such as 3 to 3.5 mm, such as 3 to 3.2 mm.

[0128] The aperture aspect ratio is not limited and may depend upon the end use of the composite. As used herein, the aperture “aspect ratio” refers to a ratio of the longest dimension to the longest dimension that runs perpendicular to the longest dimension of the aperture. For example, the aspect ratio for a rhombus (or diamond) shaped aperture would be defined as the LWO divided by the SWO as those terms are defined herein, and the aspect ratio of an elliptical- shaped aperture would be defined as the diameter of its major axis divided by its minor axis. A square or circle would have an aspect ratio of 1:1 or 1. The apertures have an aspect ratio of 1, such as at least 1.3, such as at least 1.5, such as at least 1.7, such as at least 2. The apertures may have an aspect ratio of no more than 15, such as no more than 10, such as no more than 8, such as no more than 6.5, such as no more than 5.5, such as no more than 4, such as no more than 3. The aperture may have an aspect ratio of 1 to 15, such as 1 to 10, such as 1 to 8, such as 1 to 6.5, such as 1 to 5.5, such as 1 to 4, such as 1 to 3, such as 1.3 to 15, such as 1.3 to 10, such as 1.3 to 8, such as 1.3 to 6.5, such as 1.3 to 5.5, such as 1.3 to 4, such as 1.3 to 3, such as 1.5 to 15, such as 1.5 to 10, such as 1.5 to 8, such as 1.5 to 6.5, such as 1.5 to 5.5, such as 1.5 to 4, such as 1.5 to 3, such as 1.7 to 15, such as 1.7 to 10, such as 1.7 to 8, such as 1.7 to 6.5, such as 1.7 to 5.5, suchas 1.7 to 4, such as 1.7 to 3, such as 2 to 15, such as 2 to 10, such as 2 to 8, such as 2 to 6.5, such as 2 to 5.5, such as 2 to 4, such as 2 to 3.

[0129] The metal substrate may be used as part of a composite structure. An exemplary compositive structure may comprise at least one reinforced polymer layer comprising a reinforcing material; and a layer comprising the metal substrate. Optionally, the layer comprising the metal substrate may be in direct contact with the reinforced polymer layer, and the reinforcing material optionally may be more noble than the metal substrate.

[0130] The polymer of the reinforced polymer layer may comprise any suitable thermoset or thermoplastic polymer. For example, the polymer layer may comprise an epoxy resin, a polyester resin, a vinyl ester, nylon, a polyetherketoneketone (PEKK), a polyetheretherketone (PEEK), a polyaryletherketone (PAEK), or any other suitable polymer. The polymer serves as a resin matrix for the reinforcing material.

[0131] As used herein, the term “reinforcing material” refers to materials added to a polymer matrix that enhance the strength of the polymer matrix. The reinforcing material may comprise any suitable material. For example, the reinforcing material may comprise carbon fiber, chopped fiber, non-continuous fiber, metal flake, or any combination thereof. When the reinforcing material comprises carbon fiber, the reinforced polymer layer is a carbon-fiber reinforced polymer.

[0132] The reinforcing material of the reinforced polymer layer optionally may be more noble than the metal substrate. As used herein, the term “more noble” means the reinforcing material has a higher nobility than the metal substrate as determined by the galvanic activity of each. For example, the activity or nobility of a reinforcing material and metal substrate may be determined by reference to the galvanic series, which ranks metal / metal alloys according to their electrochemical potential with reference to a standard electrode, as understood by one skilled in the art. An example of such galvanic series is provided in Atlas Steels’ Atlas TECH NOTE NO. 7, “Galvanic Corrosion,” August 2010 (with reference to a Standard Calomel Electrode (S.C.E.)). In determining the relative galvanic activity of the reinforcing material and the metal substrate, the same scale should be used.

[0133] The composite structure may optionally further comprise a surfacing film. As used herein, the term “surfacing film” refers to a resinous film that may be applied to the outermost surface of a material to improve the surface quality of the material. For example, thesurfacing film may be applied to a composite structure such that the surfacing layer is in contact with the mold used to form the composite part. The surfacing film may improve the quality of the surface of the formed composite structure to result in a smoother surface of a molded composite part that requires minimal surface finishing before the application of the decorative coating(s). The surfacing film may be either fully or partially impregnated with thermoplastic or uncured thermosetting resin.

[0134] The surfacing film may comprise any suitable surfacing film. For example, the surfacing film may comprise a resin comprising a curable resin or a thermoplastic resin. For example, the surfacing film may comprise a curable epoxy resin; curable chain-extended epoxy resin; a urethane modified epoxy resin; a CTBN modified epoxy resin; a phenoxy resin; a micronized phenoxy resin; a phenolic hardener; a polyester resin, a vinyl ester; nylon; a polyetherketoneketone (PEKK); a polyetheretherketone (PEEK); a polyaryletherketone (PAEK); any other suitable polymer; or any combination thereof.

[0135] The surfacing film may optionally further comprise a core-shell rubber toughening agent.

[0136] The resin of the surfacing film may be the same or different than the polymer of the reinforced polymer layer.

[0137] The surfacing film may optionally comprise an electrically conductive layer, such as a metal layer, which may optionally be a foil, a stamped foil, a sheet, a mesh, an expanded metal, a perforated metal, a woven metal, a grid, sintered particles, sintered felt, cloth, wires, or a combination thereof. The metal layer may be the same or different than the metal substrate described above.

[0138] The curable surfacing film may have any suitable thickness, such as, for example, between 0.025 and 1.0 mm.

[0139] The layered construction of the composite structure that includes the surfacing film may be made by any suitable method. For example, a curable surfacing film and a curable polymeric composite may be laid up, in that order, in a tool having a shape which is the inverse of the desired shape of the composite structure, and the curable surfacing film and reinforced polymer layer may be cured. Curing may be accomplished by, for example, application of heat, and optionally may be carried out under sub-atmospheric pressure, such as less than 90% of one atmosphere, such as less than 50% of one atmosphere, such as less than 10% of one atmosphere.Optionally, the composite structure may be further subjected to other optional processes such as pressure treatment using an autoclave (with vacuum bag) or a debulking process.

[0140] The present disclosure is also directed to a surfacing film comprising the metal substrate, described above.

[0141] The composite structure may comprise any suitable structure. For example, the composite structure may comprise an aircraft airframe; an external structure mounted to an aircraft; an aircraft propeller; an aircraft rotor; a helicopter or helicopter component; a rocket fuel tank; a land motor vehicle body; a marine vessel; a marine vessel component; a marine structure; a land structure; or a windmill or windmill components, among other structures.

[0142] Candidate locations and structures for use of the composite structure as a lightning strike protection material include: airframe (particularly skin portions thereof) including fuselage, wings, stabilizers, and their subcomponents; external structures (e.g., engine nacelles, external fuel tanks, external weapon pods, electronic pods, or other pods); internal structures (e.g., fuel tanks, equipment housings); propellers; and rotors. Similar uses may attend composite land vehicles or water vessels or windmill components (e.g., blades). Non-lightning applications may include radiofrequency isolation / containment (e.g., Faraday cages). When used to make any such otherwise conventional product, existing or yet-developed manufacturing techniques and basic materials may be used to which the exemplary composite structure is added.

[0143] The metal substrate of the composite structure may also be used as a resistive- heating layer. The term “resistive-heating” is used herein to indicate heat is generated via a Joule heating in which the passage of an electric current through the metal substrate produces heat. The power of heating generated by resistive-heating of the metal substrate is proportional to the product of its electrical resistance and the square of the electric current. The resistive- heating layer may be used as, for example, part of a de-icing system for an aircraft, helicopter, or windmill, among other uses.

[0144] The present disclosure is also directed to a method of making a composite structure, the method comprising fixedly adhering the treated metal substrate to at least one reinforced polymer layer comprising a reinforcing material, wherein the treated metal substrate is in direct contact with the reinforced layer, and the reinforcing material is more noble than the metal substrate.

[0145] The present disclosure is also directed to the treated metal substrate disclosed herein comprising a current collector.

[0146] The present disclosure is also directed to the treated metal substrate disclosed herein comprising a part of a proton exchange membrane (PEM) electrolyzer. For example, the treated metal substrate may comprise a current collector in electrochemical energy conversion systems, such as a proton exchange membrane electrolyzer, alkaline water electrolyzer, flow battery, carbon dioxide electrolyzer, a rechargeable secondary battery, or aqueous batteries.

[0147] It has been surprisingly discovered that the aqueous treatment composition and method of treating a substrate disclosed herein allow for the production of a part of a current collector having good resistance to corrosion resulting in low resistivity. Without intending to be bound by theory, it is believed that the aqueous treatment composition selectively increases the total titanium content at the surface of the metal substrate, reduces impurities including oxides (e.g., such as TiO2 for titanium metal substrates) and other cations such as sodium, potassium, or lithium that may result in increased resistivity at the surface of the metal substrate, and introduces a conductive titanium hydride component into the passive layer. Furthermore, a noticeable change of the metal substrate surface morphology is observed, as shown in Figure 2 and discussed further in the Examples section.

[0148] It has been further surprisingly discovered that the substrate treated with the aqueous treatment layer can be subsequently coated with a metal-containing coating, such as a platinum-containing coating or a niobium-containing coating, using the pretreatment composition disclosed herein resulting in even further improved corrosion protection resulting in low resistivity and lasting conductivity of the treated substrate.

[0149] Whereas specific aspects of the disclosure have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosure which is to be given the full breadth of the claims and aspects appended and any and all equivalents thereof. Aspects

[0150] Aspect 1. An aqueous treatment composition comprising: more than 0.0% by weight and up to 28% by weight of a fluorometallic acid, such as up to 25% by weight, suchas up to 20% by weight, such as up to 15% by weight, such as up to 10% by weight, such as up to 7% by weight, such as up to 5% by weight, based on the total weight of the composition; and a fluoride salt, such as ammonium bifluoride; wherein the aqueous treatment composition comprises less than 30% by weight nitric acid, such as less than 25% by weight, such as less than 20% by weight, such as less than 15% by weight, such as less than 10% by weight, such as less than 5% by weight, such as less than 1% by weight, based on the total weight of the composition.

[0151] Aspect 2. An aqueous treatment composition comprising: more than 0.0% by weight and up to 5% by weight of a fluorometallic acid, based on the total weight of the composition, such as in an amount of at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight, such as at least 4% by weight; and a fluoride salt, such as ammonium bifluoride.

[0152] Aspect 3. An aqueous treatment composition comprising: an acid, such as a fluorometallic acid; free fluoride in an amount of at least 2 ppm, such as at least 10 ppm based on total weight of the composition, such as at least 25 ppm, such as at least 35 ppm, such as at least 100 ppm, such as at least 200 ppm; and total fluoride in an amount of at least 50 ppm based on total weight of the pretreatment composition, such as at least 75 ppm, such as at least 100 ppm.

[0153] Aspect 4. An aqueous treatment composition comprising: more than 0.0% by weight and up to 28% by weight of an acid, such as a fluorometallic acid, such as up to 25% by weight, such as up to 20% by weight, such as up to 15% by weight, such as up to 10% by weight, such as up to 7% by weight, such as up to 5% by weight, based on the total weight of the composition; free fluoride in an amount of at least 2 ppm, such as at least 10 ppm based on total weight of the composition, such as at least 25 ppm, such as at least 35 ppm, such as at least 100 ppm, such as at least 200 ppm; and total fluoride in an amount of at least 50 ppm based on total weight of the pretreatment composition, such as at least 75 ppm, such as at least 100 ppm; wherein the aqueous treatment composition comprises less than 30% by weight nitric acid, such as less than 25% by weight, such as less than 20% by weight, such as less than 15% by weight, such as less than 10% by weight, such as less than 5% by weight, such as less than 1% by weight, based on the total weight of the composition.

[0154] Aspect 5. An aqueous treatment composition comprising: more than 0.0% by weight and up to 5% by weight of a fluorometallic acid, based on the total weight of the composition, such as in an amount of at least 0.5% by weight, such as at least 1% by weight,such as at least 2% by weight, such as at least 3% by weight, such as at least 4% by weight; free fluoride in an amount of at least 2 ppm, such as at least 10 ppm based on total weight of the composition, such as at least 25 ppm, such as at least 35 ppm, such as at least 100 ppm, such as at least 200 ppm; and total fluoride in an amount of at least 50 ppm based on total weight of the pretreatment composition, such as at least 75 ppm, such as at least 100 ppm.

[0155] Aspect 6. The aqueous treatment composition of any of aspects 1, 3, or 4, wherein the fluorometallic acid is present in an amount of at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight, such as at least 4% by weight, such as at least 5% by weight, such as at 10% by weight, such as at least 15% by weight, such as at least 20% by weight, such as at least 25% by weight, based on the total weight of the composition.

[0156] Aspect 7. The aqueous treatment composition of any of the preceding aspects, wherein the metal in the fluorometallic acid comprises, consists essentially of, or consists of, a Group IIIA metal, a Group IVA metal, a Group IVB metal, and / or a Group VIII metal.

[0157] Aspect 8. The aqueous treatment composition of any of the preceding aspects, wherein the fluoride in the fluorometallic acid has a mole ratio to the Group IIIA metal, Group IVA metal, Group IVB metal, Group VI metal, and / or Group VIII metal of more than 4.

[0158] Aspect 9. The aqueous treatment composition of any of the preceding aspects, wherein the fluorometallic acid comprises, consists essentially of, or consists of hexafluorosilicic acid.

[0159] Aspect 10. The aqueous treatment composition of any of the preceding aspects, wherein the fluoride salt is present in an amount of at least 0.1% by weight, based on the total weight of the composition, such as at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight; and / or the fluoride salt is present in an amount of no more than 38% by weight, such as no more than 20% by weight, such as no more than 15% by weight, such as no more than 10% by weight, such as no more than 7% by weight, such as no more than 5% by weight, such as no more than 4% by weight, such as no more than 3.5% by weight.

[0160] Aspect 11. A method of treating a metal substrate comprising contacting at least a portion of the metal substrate with the aqueous treatment composition of any of the preceding aspects.

[0161] Aspect 12. The method of aspect 11, wherein the metal substrate comprises titanium and / or a titanium alloy.

[0162] Aspect 13. The method of aspect 11 or 12, wherein the metal substrate comprises a foil, a stamped foil, or a porous metal substrate, such as a mesh, an expanded metal, a perforated metal, a woven metal, a grid, sintered particles, sintered felt, or a combination thereof.

[0163] Aspect 14. A metal substrate comprising at least a portion of its surface treated with one of the aqueous treatment compositions of any of aspects 1-10.

[0164] Aspect 15. A metal substrate treated according to the method of aspect 11, 12, or 13.

[0165] Aspect 16. The metal substrate of aspect 14 or 15, wherein the ratio of the percentage of Ti3+to the percentage of Ti2+of the metal substrate as measured using high resolution X-ray photoelectron spectroscopy is at least 0.7, such as at least 0.9, such as at least 1, such as at least 1.2, such as at least 1.4, such as at least 1.6, such as at least 1.8, such as at least 2, such as at least 2.1, such as at least 2.2.

[0166] Aspect 17. The metal substrate of any of aspects 14-16, wherein the total percentage of titanium present on the surface of the metal substrate treated with the aqueous treatment composition is at least 2% greater than the total percentage of titanium present on the surface of the metal substrate prior to treatment, such as at least 4% greater, such as at least 6% greater, such as at least 8% greater.

[0167] Aspect 18. The metal substrate of any of aspects 14-17, wherein the percentage of Ti3+present on the surface of the metal substrate treated with the aqueous treatment composition is at least 1% greater than the percentage of Ti3+present on the surface of the metal substrate prior to treatment, such as at least 2% greater, such as at least 3% greater, such as at least 4% greater.

[0168] Aspect 19. The metal substrate of any of aspects 14-18, wherein the percentage of Ti2+present on the surface of the metal substrate treated with the aqueous treatment composition is at least 2% less than the percentage of Ti2+present on the surface of themetal substrate prior to treatment, such as at least 4% less, such as at least 6% less, such as at least 8% less.

[0169] Aspect 20. The metal substrate of any of aspects 14-19, wherein the surface crystallinity using grazing incidence X-ray diffraction to determine the (101):(002) reflection ratio of the surface of the metal substrate treated with the aqueous treatment composition is at least 5% less than the surface of the metal substrate prior to treatment, such as at least 10% less, such as at least 15% less, such as at least 20% less.

[0170] Aspect 21. The metal substrate of any of aspects 14-20, wherein the roughness of the surface of the metal substrate treated with the aqueous treatment composition is at least 1.3 times rougher than the surface prior to treatment, such as at least 1.5 times rougher, such as at least 1.8 times rougher, such as at least 2 times rougher, such as at least 2.2 times rougher, such as at least 2.4 times rougher, such as at least 2.6 times rougher.

[0171] Aspect 22. The metal substrate of any of aspects 14-21, wherein the metal substrate treated with the aqueous treatment composition has an interfacial contact resistivity of less than 5 mΩ cm2, such as less than 3 mΩ cm2, such as less than 1 mΩ cm2, as measured according to the ICR TEST METHOD.

[0172] Aspect 23. The metal substrate of any of aspects 14-22, wherein the metal substrate treated with the aqueous treatment composition has an interfacial contact resistivity growth of less than 20 mΩ cm2 / h after 100 hours of electrochemical oxidation exposure, such as less than 15 mΩ cm2 / h, such as less than 10 mΩ cm2 / h, such as less than 5 mΩ cm2 / h, such as less than 3 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0173] Aspect 24. The metal substrate of any of aspects 14-23, wherein the metal substrate treated with the aqueous treatment composition has an interfacial contact resistivity growth of less than 40 mΩ cm2 / h after 250 hours of electrochemical oxidation exposure, such as less than 35 mΩ cm2 / h, such as less than 30 mΩ cm2 / h, such as less than 25 mΩ cm2 / h, such as less than 20 mΩ cm2 / h, such as less than 15 mΩ cm2 / h, such as less than 10 mΩ cm2 / h, such as less than 5 mΩ cm2 / h, such as less than 3 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0174] Aspect 25. The metal substrate of any of aspects 14-24, wherein the metal substrate treated with the aqueous treatment composition has an interfacial contact resistivitygrowth of less than 40 mΩ cm2 / h after exposure of the substate to thermal oxidation testing, such as less than 35 mΩ cm2 / h, such as less than 30 mΩ cm2 / h, such as less than 25 mΩ cm2 / h, such as less than 20 mΩ cm2 / h, such as less than 15 mΩ cm2 / h, such as less than 10 mΩ cm2 / h, such as less than 5 mΩ cm2 / h, such as less than 3 mΩ cm2 / h, as measured according to the ICR THERMAL OXIDATION TEST METHOD.

[0175] Aspect 26. The metal substrate of any of aspects 14-25, wherein the metal substrate treated with the aqueous treatment composition has a TOF-SIMs depth profile for H+ / Ti+ relative ion intensity inverse peak within 0-5 nm depth of at least 0.002, such as at least 0.003, such as at least 0.004.

[0176] Aspect 27. The metal substrate of any of aspects 14-26, wherein the metal substrate treated with the aqueous treatment composition has a TOF-SIMs depth profile for Na+ / Ti+relative ion intensity inverse peak within 0.5 nm depth of no more than 3.2, such as no more than 3, such as no more than 2.5, such as no more than 2, such as no more than 1.5, such as no more than 1.

[0177] Aspect 28. The metal substrate of any of aspects 14-27, wherein the metal substrate comprises titanium or a titanium alloy.

[0178] Aspect 29. A pretreatment composition comprising: an acid; a source of a metal comprising vanadium, manganese, nickel, silicon, ruthenium, rhodium, palladium, gold, tin, tantalum, tungsten, iridium, silver, mercury, thallium, lead, bismuth, polonium, platinum, niobium, titanium, cerium, or a combination thereof; a source of free fluoride; and an aqueous medium, wherein the acid, the source of the metal, and the source of free fluoride are each different components.

[0179] Aspect 30. The pretreatment composition of aspect 29, wherein the acid comprises a fluorometallic acid.

[0180] Aspect 31. The pretreatment composition of aspect 29, wherein the metal in the fluorometallic acid comprises, consists essentially of, or consists of, a Group IIIA metal, a Group IVA metal, a Group IVB metal, and / or a Group VIII metal.

[0181] Aspect 32. The pretreatment composition of aspect 30 or 31, wherein the fluoride in the fluorometallic acid has a mole ratio to the Group IIIA metal, Group IVA metal, Group IVB metal, Group VI metal, and / or Group VIII metal of more than 4.

[0182] Aspect 33. The pretreatment composition of any of the preceding aspects 29- 32, wherein the acid comprises, consists essentially of, or consists of hexafluorosilicic acid.

[0183] Aspect 34. The pretreatment composition of any of the preceding aspects 29- 33, wherein the acid is present in an amount of at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight, such as at least 4% by weight, such as at least 5% by weight, such as at 10% by weight, such as at least 15% by weight, such as at least 20% by weight, such as at least 25% by weight, based on the total weight of the composition.

[0184] Aspect 35. The pretreatment composition of any of the preceding aspects 29- 34, wherein the pretreatment composition comprises free fluoride in an amount of at least 2 ppm, such as at least 10 ppm based on total weight of the composition, such as at least 25 ppm, such as at least 35 ppm, such as at least 100 ppm, such as at least 200 ppm.

[0185] Aspect 36. The pretreatment composition of any of the preceding aspects 29- 35, wherein the pretreatment composition comprises total fluoride in an amount of at least 50 ppm based on total weight of the pretreatment composition, such as at least 75 ppm, such as at least 100 ppm.

[0186] Aspect 37. The pretreatment composition of any of the preceding aspects 29- 36, wherein the source of free fluoride comprises a fluoride salt, such as ammonium bifluoride.

[0187] Aspect 38. The pretreatment composition of aspect 37, wherein the fluoride salt is present in an amount of at least 0.1% by weight, based on the total weight of the composition, such as at least 0.5% by weight, such as at least 1% by weight, such as at least 2% by weight, such as at least 3% by weight; and / or the fluoride salt is present in an amount of no more than 38% by weight, such as no more than 20% by weight, such as no more than 15% by weight, such as no more than 10% by weight, such as no more than 7% by weight, such as no more than 5% by weight, such as no more than 4% by weight, such as no more than 3.5% by weight.

[0188] Aspect 39. The pretreatment composition of any of the preceding aspects 29- 38, wherein the metal comprises, consists essentially of, or consists of niobium.

[0189] Aspect 40. The pretreatment composition of any of the preceding aspects 29- 39, wherein the source of the metal comprises, consists essentially of, or consists of ammonium niobium oxalate, niobium oxide, niobium oxide hydrate, or a combination thereof.

[0190] Aspect 41. The pretreatment composition of any of the preceding aspects 29- 38, wherein the metal comprises, consists essentially of, or consists of platinum.

[0191] Aspect 42. The pretreatment composition of any of the preceding aspects 29- 38, wherein the source of the metal comprises, consists essentially of, or consists of chloroplatinic acid, potassium hexachloroplatinate, ammonium hexachloroplatinate(IV), potassium tetrachloroplatinate(II), ammonium tetrachloroplatinate(II), platinum (IV) chloride, platinum(II) chloride , tetraamineplatinum(II)nitrate, platinum (IV) nitrate, platinum (II) sulfate, or a combination thereof.

[0192] Aspect 43. The pretreatment composition of any of the preceding aspects 29- 42, wherein the source of the metal is present in an amount such that solubilized metal is present in an amount of at least 100 ppm, such as at least 500 ppm, such as at least 1,000 ppm, such as at least 1,500 ppm, such as at least 2,000 ppm, such as at least 2,500 ppm, such as at least 3,000 ppm, such as at least 3,500 ppm, such as at least 4,000 ppm, such as at least 4,500 ppm, such as at least 5,000 ppm, such as at least 5,500 ppm, such as at least 6,000 ppm, such as at least 6,500 ppm, such as at least 7,000 ppm, such as at least 7,500 ppm, such as at least 8,000 ppm, such as at least 8,500 ppm, such as at least 9,000 ppm, such as at least 9,500 ppm, such as at least 10,000 ppm, such as at least 10,500 ppm, and / or the source of the metal is present in an amount such that solubilized metal is present in an amount of no more than 13,000 ppm, such as no more than 11,000 ppm, such as no more than 10,000 ppm, such as no more than 9,000 ppm, such as no more than 8,000 ppm, such as no more than 7,000 ppm, such as no more than 6,000 ppm, such as no more than 5,000 ppm, such as no more than 4,000 ppm, such as no more than 3,000 ppm, such as no more than 2,000 ppm, such as no more than 1,000 ppm.

[0193] Aspect 44. The method of any of aspects 11-13, wherein the method further comprises contacting at least a portion of the metal substrate with the pretreatment composition of any of the preceding aspects 29-43.

[0194] Aspect 45. The method of aspect 44, wherein the method further comprises (1) heating the pretreatment composition to a temperature of 30°C to 60°C, such as 30°C to 50°C, such as 35°C to 45°C, and / or (2) stirring the pretreatment composition during contacting the metal substrate with the pretreatment composition.

[0195] Aspect 46. A metal substrate comprising at least a portion of its surface treated with one of the aqueous treatment compositions of any of aspects 1-10 and further treated with the pretreatment composition of any of aspects 29-43.

[0196] Aspect 47. A metal substrate treated according to the method of aspect 44 or 45.

[0197] Aspect 48. The metal substrate of any of aspects 46 or 47, wherein the metal substrate treated with the aqueous treatment composition and pretreatment composition has an interfacial contact resistivity growth of less than 10 mΩ cm2 / h after 50 hours of electrochemical oxidation exposure, such as less than 5 mΩ cm2 / h, such as less than 1 mΩ cm2 / h, such as less than 0.5 mΩ cm2 / h, such as less than 0.3 mΩ cm2 / h, such as less than 0.1 mΩ cm2 / h, such as less than 0.05 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0198] Aspect 49. The metal substrate of any of aspects 46-48, wherein the metal substrate treated with the aqueous treatment composition and pretreatment composition has an interfacial contact resistivity growth of less than 10 mΩ cm2 / h after 100 hours of electrochemical oxidation exposure, such as less than 5 mΩ cm2 / h, such as less than 1 mΩ cm2 / h, such as less than 0.5 mΩ cm2 / h, such as less than 0.3 mΩ cm2 / h, such as less than 0.1 mΩ cm2 / h, such as less than 0.05 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0199] Aspect 50. The metal substrate of any of aspects 46-49, wherein the metal substrate treated with the aqueous treatment composition and pretreatment composition has an interfacial contact resistivity growth of less than 10 mΩ cm2 / h after 250 hours of electrochemical oxidation exposure, such as less than 5 mΩ cm2 / h, such as less than 1 mΩ cm2 / h, such as less than 0.5 mΩ cm2 / h, such as less than 0.3 mΩ cm2 / h, such as less than 0.1 mΩ cm2 / h, such as less than 0.05 mΩ cm2 / h, as measured according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD.

[0200] Aspect 51. The metal substrate of aspects 11-29 or 46-50, wherein the metal substrate comprises a foil, a stamped foil, a porous metal substrate, such as a mesh, an expanded metal, a perforated metal, a woven metal, a grid, sintered particles, sintered felt, or a combination thereof.

[0201] Aspect 52. The metal substrate of any of the preceding aspects 11-29 or 46-50, wherein the metal substrate comprises a part of a proton exchange membrane electrolyzer.

[0202] Aspect 53. The metal substrate of any of the preceding aspects 11-29 or 46-50, wherein the metal substrate comprises a part of a composite structure.

[0203] Aspect 54. The metal substrate of aspect 53, wherein the composite structure comprises a vehicle or vehicle part.

[0204] Aspect 55. A vehicle or vehicle part comprising the composite structure of aspect 53.

[0205] Aspect 56. An aircraft or aircraft part comprising the composite structure of aspect 53.

[0206] Aspect 57. A windmill or windmill component comprising the composite structure of aspect 53.

[0207] Aspect 58. A marine vessel or marine vessel component comprising the composite structure of aspect 53.

[0208] Aspect 59. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in an electrolyzer.

[0209] Aspect 60. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in a proton exchange membrane electrolyzer.

[0210] Aspect 61. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in an alkaline water electrolyzer.

[0211] Aspect 62. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in a carbon dioxide electrolyzer.

[0212] Aspect 63. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in a rechargeable secondary battery.

[0213] Aspect 64. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in an electrical component.

[0214] Aspect 65. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in an electrochemical storage device.

[0215] Aspect 66. Use of the metal substrate of any of the preceding aspects 11-29 or 46-50 in a flow battery.

[0216] Aspect 67. A kit comprising the aqueous treatment composition of any of aspects 1-10 and / or the pretreatment composition of any of aspects 29-43, and optionally instructions for treating a substrate with the aqueous treatment composition, the pretreatment composition, or both the aqueous treatment composition and the pretreatment composition.

[0217] Aspect 68. The kit of aspect 67, wherein the instructions comprise the method of any of aspects 11-13 or 44-45.

[0218] Illustrating the disclosure are the following examples, which, however, are not to be considered as limiting the disclosure to their details. Unless otherwise indicated, all parts and percentages in the following examples, as well as throughout the specification, are by weight. EXAMPLES

[0219] Example 1: An aqueous treatment solution containing hydrofluorosilicic acid (5 wt.%, based on the total weight of the composition) and ammonium bifluoride (3.4 wt.%, based on the total weight of the composition) at a pH of 2.5 was prepared using deionized water. A clean piece of chemically pure, grade-1 titanium approximately 1.5” x 6” with a thickness of 0.004” was submerged into this solution for 1 minute at room temperature, resulting in gas evolution and a change in solution appearance from colorless to light yellow. The treated area of the titanium was no longer lustrous and had a matte silver appearance.

[0220] Scanning electron microscopy (SEM) images were collected by mounting a small amount of sample on aluminum stubs with carbon tape. The sample was then coated with Au / Pd for 10 seconds and analyzed in the Quanta 250 FEG SEM under high vacuum. The accelerating voltage was set to 10.00 kV and the spot size was 3.0. As shown in Figure 2, the images reveal the surface morphology of the treated foil to be significantly exfoliated compared to the native foil. Complementary images were acquired using confocal laser scanning microscopy (CLSM) by taping down the samples to a CLSM stage to ensure flatness. A 3D laser microscope (Keyence VK X-200 CLSM) was used with a 50x objective for imaging. Three images were taken in three locations for each sample. Mean roughness values were extracted from height maps in Keyence MultiFileAnalyzer and averaged. This test method is referred to as the SURFACE ROUGHNESS TEST METHOD herein. Image analysis revealed that the average surface roughness of this treated area increased by 2.6 times relative to the native foil. However, the treatment imparted no change to the mechanical properties (

[0221] Table 1) or surface energy (Figure 3) of the treated area in comparison to the native titanium foil.

[0222] High resolution X-ray photoelectron spectroscopy experiments were performed using a Physical Electronics VersaProbe III instrument equipped with a monochromatic Al kα x- ray source (hν = 1,486.6 eV) and a concentric hemispherical analyzer. Charge neutralization was performed using both low energy electrons (<5 eV) and argon ions. The binding energy axis was calibrated using sputter cleaned Cu (Cu 2p3 / 2 = 932.62 eV, Cu 3p3 / 2 = 75.1 eV) and Au foils (Au 4f7 / 2 = 83.96 eV). Peaks were charge-referenced to CHx band in the carbon 1s spectra at 284.8 eV. Measurements were made at a takeoff angle of 45° with respect to the sample surface plane. This resulted in a typical sampling depth of 3-6 nm (95% of the signal originated from this depth or shallower). Quantification was done using instrumental relative sensitivity factors (RSFs) that account for the X-ray cross section and inelastic mean free path of the electrons. On homogeneous samples major elements (>5 atom%) tend to have standard deviations of <3% while minor elements can be significantly higher. The analysis size was ~200µm in diameter. This test method is referred to as the HIGH-RESOLUTION X-RAY PHOTOELECTRON SPECTROSCOPY TEST METHOD herein. As detailed in Table 2, the high-resolution X-ray photoelectron spectroscopy experiment revealed that the treated surface contained 8% more exposed titanium compared to untreated titanium surface. Peak fitting of the titanium region showed that the treated sample contained 4% more Ti3+and 8% less Ti2+compared to un-treated titanium.

[0223] Lastly the surface crystallinity was studied using grazing incidence X-ray diffraction (GIXRD), which was collected from 10 to 70° 2θ using a Malvern Panalytical Empyrean® instrument fitted with a copper long-fine-focus X-ray tube operated at 45 kV and 40 mA. The incident beam path included a parallel beam X-ray mirror and a 0.5° divergence slit fixed at an incident angle of 1°. The diffracted beam path incorporated dCore® optics with a 0.28° parallel plate collimator and a PIXcel3D® detector operating in open detector (0D) mode with an active length of 14.025 mm. Data were collected with a nominal step size of 0.026° 2θ. The pulse height distribution (PHD) settings lower and upper levels were set at 4.02 and 11.27 keV respectively. This test method is referred to as the X-RAY DIFFRACTION TEST METHOD herein. The GIXRD patterns are shown in Figure 4, which demonstrates that the (101):(002) reflection ratio of titanium metal changes from 1.11 to 0.87 following treatment.Table 1 Mechanical Property Before Treatment After Treatment Modulus (GPa) 70 ± 1 69 ± 1a e Sample Titotal(%) Normalized Normalized Normalized Normalized Ti4+(%) Ti3+(%) Ti2+(%) Ti0(%)

[0224] Example 2: The ability of the treated titanium (as in Example 1) and un-treated titanium to resist electrochemical oxidation was evaluated by submerging the foils into pH 3 sulfuric acid and applying 2.4 V vs. NHE. After either 100 or 250 hours of electrolysis, the titanium foil was rinsed with deionized water and dried under a nitrogen steam. The interfacial contact resistivity (ICR) of these foils was evaluated using copper electrodes affixed to Teflon blocks compressed to either 300 or 1000 psi. A current density of 62 mA / cm2was applied across these foils and the resulting voltage drop measured. A similar measurement was made using the copper electrodes only, and the difference between these two values multiplied by the measurement area (1.6 cm2) yields the ICR, shown in Figure 5. This test procedure is referred to as the ICR ELECTROCHEMICAL OXIDATION TEST METHOD herein, and the initial measurement before exposure to electrochemical oxidation is referred to as the ICR TEST METHOD. Untreated titanium foil was found to have a significant increase in ICR upon 100 and 250 h of electrolysis (as well as a higher baseline measurement at 0 hours), while the treated titanium foil showed a small increase in ICR during the first 100h, but no significant further increase after 250 hours. The scanning electron microscopy images shown in Figure 6 supports these results, by the appearance of small crystallites on the untreated titanium, not present on the treated foil. This crystallite morphology is consistent with the formation of insulating TiO2. X- ray photoelectron spectroscopy further supports the reduced formation of TiO2 in the treatedsample, as ~9% of the titanium on the surface was in a reduced state, compared to ~4% on the untreated foil, as shown in Table 3. Table 3 Sample Titotal(%) Normalized Normalized Normalized Normalized Ti4+(%) Ti3+(%) Ti2+(%) Ti0(%)[ ] xamp e : er rea men ou ne n xamp e , e o s were eva ua e or their resistance to thermal oxidation. Untreated and treated foils were placed in a box furnace and were heated to 400°C under air and left at that temperature for one hour. Once the foils were cooled, the untreated foil had a purple appearance, while the treated foil was a golden color. Using the setup described in Example 3 the ICR of both treated and un-treated foil after exposure to high temperature was evaluated. This test procedure is referred to as the ICR THERMAL OXIDATION TEST METHOD herein. As shown in Figure 7, the treated foil retained a low ICR of < 5 mΩ cm2while the ICR of the un-treated foil increased significantly to near 40 mΩ cm2after heat treatment.

[0226] Example 4: Time of flight secondary ion mass spectrometry (TOF-SIMs) was used to further elucidate how this treatment affects titanium surface composition. This technique pairs compositional characterization with depth profiling allowing us to evaluate how the material composition evolves with depth from the surface. The depth profile analysis utilized a low energy 500 eV O2+beam for sample erosion and a high energy Bi32+beam for sample interrogation. Successive etch and analyze cycles were utilized to remove material (typically nm’s at a time) with the low energy oxygen beam, then analyze the sample by monitoring the ionic species generated after Bi cluster bombardment in the mass spectrometer. The sample etch rate is established based off of SiO2sputter rate of an SiO2 / Si film with a 5nm oxide layer. Two different etch areas were utilized during the analysis, 500x500 µm2and 1000x1000 µm2. For the 500x500 µm2area, the etch rate is approximated to be 0.21 nm per etch cycle, whereas the 1000x1000 µm2sputter area is approximated to be ~0.167 nm / cycle. These two areas were used for comparison due to the high roughness of the treated samples; the large areas were chosen to make sure that the sputtered area was significantly large enough to not encompass all feature sizes so as not to preferentially analyze one feature over another. The interrogation area wasconsistently 50x50 µm2and always remained at the center of the etch crater. A comparison of the surface roughness between the control Ti coupon shows variation in surface roughness - which will affect the depth-measurements’ reported values - making them likely to be not as precise resulting in the reported depth-measurements being presented provided as estimated depth. Figure 8 displays the measured relative intensity of positive hydrogen ions (H+) to positive titanium ions at various estimated depths. This analysis suggests the titanium surface composition modification by an increase in the H+ / Ti+ratio from a minimum value of 0.0015 in the unmodified titanium control compared to the two treated samples, which displays a H+ / Ti+minimum value double that of the control between 0.003-0.004. The hydrogen content in all samples increases after this point, sharply for the uncoated titanium and at a much more modest rate for the two treated samples. This change in growth rate is attributed to the increased sample roughness for the treated samples as shown in Error! Reference source not found.2B. The increased hydrogen content in the top 5 nm of the treated samples point to hydrogen incorporation into the titanium oxide layer. Hydrogen may be incorporated in the form of titanium hydride, which is characterized by higher electrical conductivity compared to titanium oxide, explaining the reduced interfacial contact resistance values measured after treatment in Figure 5. This test procedure is referred to as the TOF-SIMs TEST METHOD.

[0227] In addition to evaluating the hydrogen content in comparison to titanium, the TOF-SIMs analysis revealed that the titanium treatment solution has a direct effect on the concentration of alkali cation, such as sodium, as shown in Figure 9. In both treated samples tested, the detectable sodium content was decreased relative to the unmodified titanium control sample at all measured depth values. The decreased amount of alkali metals may indicate that the control sample has a more amorphous surface with more cation defects. The presence of a more amorphous surface is supported by the SEM images shown in Error! Reference source not found.A and 2B, which demonstrate that before treatment the titanium surface is characterized visually by a more amorphous material compared to the highly ordered surface state present after treatment.

[0228] Example 5: A series of treatment solutions containing ammonium bifluoride (3.4 wt.%, based on the total weight of the composition) at a pH of 2.5 were prepared using various different acids. The acids used include fluorosilicic acid (4 wt.%, based on the total weight of the composition), fluorozirconic acid (6 wt.%, based on the total weight of the composition),phosphoric acid (19 wt.%, based on the total weight of the composition), sulfuric acid (5 wt.%, based on the total weight of the composition), nitric acid (4 wt.%, based on the total weight of the composition), and hydrochloric acid (2 wt.%, based on the total weight of the composition). A clean piece of chemically pure, grade-1 titanium approximately 1.5” x 6” with a thickness of 0.004” was submerged into this solution for 1 minute, resulting in gas evolution and a change in solution appearance from colorless to light yellow. The treated area of the titanium is no longer lustrous and has a matte silver appearance in all cases. Following DI water rinsing and air drying, the interfacial contact resistivity (ICR) of these foils was evaluated using copper electrodes affixed to Teflon blocks compressed to 400 psi. Subsequently, each foil was immersed in pH 3 sulfuric acid and electrolyzed at 2.4 V vs. NHE for 50 h. Following electrolysis, the foils were rinsed, dried and their ICR measured again. The difference between the ICR after 50 h of electrolysis and its initial ICR is reported in Figure 10 as the ICR growth rate. All foils that have been treated show significantly lower ICR growth rates compared to those without treatment. However, there is a dependence on acid identity and ICR growth rate. In particular, the ICR of nitric acid containing solutions grows at a rate of 0.17 mΩ cm2h-1compared to fluorosilicic acid solutions which display an ICR growth rate of 0.04 mΩ cm2h-1. These results highlight that the acid anion may participate in this process. The nitrate anion for instance may be reduced to nitrite or other reduced nitrogen species by the highly reducing titanium surface exposed during treatment.

[0229] Example 6: A pretreatment composition with 10,000 ppm Nb was prepared by dissolving ammonium niobate oxalate hydrate (1.63 wt%, based on the total weight of the composition), oxalic acid (1 wt%, based on the total weight of the composition), and ammonium bifluoride (0.6 M) in DI water at a pH of 5. A clean piece of chemically pure, grade-1 titanium approximately 1.5” × 6” with a thickness of 0.004” substrate was treated using the treatment solution and method outlined in Example 1 followed by DI water rinsing and air drying for 1 minute. The substrate was then submerged into the pretreatment composition having 10,000 ppm Nb treatment solution for 1 minute resulting in gas evolution. The treated foils did not change appearance drastically compared with titanium treated by the first treatment solution only. X-ray fluorescence spectroscopy (XRF) was collected at a 50 kV voltage, 30 μA current with a measurement duration of 240 seconds. XRF spectra in Figure 11 displays the XRF spectra of the titanium substrate treated with only the first treatment solution (dotted) comparedto the substrate further treated with the niobium-containing pretreatment composition (solid) with the reference lines indicating the Nb Kα1 and Kα2 signals indicating the presence of a niobium-containing coating on the titanium substrate treated with the niobium-containing pretreatment composition. The foil was then immersed in pH 3 sulfuric acid and a 2.4 V vs. NHE electrolysis was applied according to the ICR ELECTROCHEMICAL OXIDATION TEST METHOD. The ICR growth rate was 0.013 mΩ∙cm2 / h after 50 hours electrolysis for the substrate treated with the first treatment solution and the niobium-containing pretreatment composition, whereas the titanium substrate treated only with the first treatment solution displayed an ICR growth rate of 0.045 mΩcm2 / h under the same conditions indicating a further improvement in the substate treated with the niobium-containing pretreatment composition.

[0230] Example 7: A platinum treatment solution was prepared by dissolving chloroplatinic acid (1 wt%, based on the total weight of the composition), oxalic acid (0.3M), and ammonium bifluoride (0.06 M) in DI water. A clean piece of chemically pure, grade-1 titanium approximately 1.5” × 6” with a thickness of 0.004” was treated using the treatment solution and method outlined in example 1 followed by DI water rinsing and air drying for 1 minute. The substrate was then submerged into the platinum pretreatment composition for 2 minutes with no noticeable change. The treated foils were slightly darker in appearance than when treated by the first treatment solution only. X-ray fluorescence spectroscopy (XRF) was collected at a 40 kV voltage, 9 μA current with a measurement duration of 30 seconds, to confirm platinum deposition as shown in Figure 12. Top-down scanning electron microscopy supports the deposition of platinum by the appearance of spherical particles as shown in Figure 13. Image analysis was performed by thresholding each image and determining the % of white pixels to uncover a platinum surface coverage of 6-10%. The foil was then immersed in pH 3 sulfuric acid and a 2.4 V vs. NHE electrolysis was applied. The ICR growth rate was 0.001 mΩ∙cm2 / h after 50 hours electrolysis, compared to uncoated titanium which under the same electrolysis conditions displays an ICR growth rate of 1.36 mΩcm2 / h.

[0231] Example 8: A fluoride-containing oxalic acid treatment solution was prepared by dissolving 9.26 g of oxalic acid dihydrate and 0.86 g of ammonium bifluoride in DI water and diluting to 250 mL with additional DI water. A platinum pretreatment composition was prepared by dissolving chloroplatinic acid (1 wt%, based on the total weight of the composition), oxalic acid (0.3M), and ammonium bifluoride (0.06 M) in DI water. A clean piece of chemically pure,grade-1 titanium approximately 1.5” × 6” with a thickness of 0.004” was treated by submerging the foil in the aqueous treatment solution containing hydrofluorosilicic acid (5 wt.%, based on the total weight of the composition) and ammonium bifluoride (3.4 wt.%, based on the total weight of the composition) at a pH of 2.5 as described in Example 1 for 1 minute with gas evolution beginning several seconds after the foil is introduced, followed by an immediate submersion into the fluoride-containing oxalic acid treatment solution for 10 seconds during which gas evolution continued, then immediately followed by submerging in the platinum pretreatment composition described above for two minutes. In this last step of platinum deposition, only a brief burst of gas was observed, then the bubbles ceased and the titanium surface darkened. X-ray fluorescence spectroscopy (XRF) was collected at a 40 kV voltage, 9 μA current with a measurement duration of 30 seconds to confirm platinum deposition as shown in Figure 14. Top-down scanning electron microscopy supports the deposition of platinum by the appearance of a large, relatively uniform distribution of small spherical particles as shown in Figure 15. Image analysis was performed by thresholding each image and determining the % of white pixels to uncover a platinum surface coverage of 86-91%. The foil was then immersed in pH 3 sulfuric acid and a 2.4 V vs. NHE electrolysis was applied. The ICR growth rate was 0.002 mΩ∙cm2 / h after 50 hours electrolysis, compared to uncoated titanium which under the same electrolysis conditions displays an ICR growth rate of 1.36 mΩcm2 / h.

[0232] Example 9: A 0.2 M ammonium bifluoride aqueous treatment solution was prepared by dissolving 2.85 g of ammonium bifluoride in 200 mL of water, followed by the addition of 12.75 g of a 23 wt% fluorosilicic acid solution in water to adjust the pH to 2.5. Afterward, the solution was diluted further with water to 250mL of total solution. Separately, an ammonium niobate oxalate pretreatment composition was prepared by dissolving 9 g of ammonium niobate oxalate hydrate into 100 g of DI water. The ammonium niobate oxalate solution was then heated to 50℃. A clean piece of chemically pure, grade-1 titanium approximately 1.5” × 6” with a thickness of 0.004” was treated using the 0.2 M ammonium bifluoride aqueous treatment solution at pH 2.4 for 90 seconds, followed by a rinse with DI water and then drying under a stream of air. A second treatment was completed on the titanium foil in the ammonium niobate oxalate pretreatment composition at 50℃ for 5 minutes. Afterward, the foil was rinsed with DI water and dried under a stream of air. The foil was then immersed in pH3 sulfuric acid and a 2.4 V vs. NHE was applied. The ICR growth rate was 0.011 mΩ∙cm2 / h and 0.009 mΩ∙cm2 / h after 50 and 100 hours electrolysis, respectively.

[0233] The ICR growth rate for all of the described treatments is shown in Figure 16. The described treatments all are shown to reduce the ICR growth rate from anywhere from 1-3 orders of magnitude, based on the specific formulations and applications method.

[0234] Example 10: A platinum treatment solution was prepared by dissolving chloroplatinic acid (1 wt%, based on the total weight of the composition), oxalic acid (0.3 M), and ammonium bifluoride (0.06 M) in DI water. A clean piece of chemically pure, grade-1 expanded titanium mesh approximately 2” × 4” with a thickness of 0.01” was treated using the treatment solution and method outlined in Example 1 followed by DI water rinsing. The substrate was then submerged into the platinum pretreatment solution and subjected to constant voltage 1.5 V using 316 stainless steel mesh as counter electrode for 2.5 min at room temperature. The treated foils subjected to the platinum pretreatment solution treatment were darker and more dull in appearance than when treated by the first treatment solution only. X-ray fluorescence spectroscopy (XRF) was collected at a 40 kV voltage, 10 μA current with a measurement duration of 30 seconds, to confirm platinum deposition as shown in Figure 17. Top-down scanning electron microscopy supports the deposition of platinum by the appearance of spherical particles as shown in Figure 18. Image analysis was performed by thresholding 20 images with a yellow filter and determining the % of yellow pixels to uncover a platinum average surface coverage of 58%.

[0235] Example 11: A 0.06 M ammonium bifluoride aqueous treatment solution was prepared by dissolving 0.855 g of ammonium bifluoride in 200 mL of water followed by the addition of 5.33 g of a 23 wt% fluorosilicic acid solution in water to adjust the pH to 2.5. Afterward the solution was diluted further with water to 250 mL.

[0236] Separately, a gold pretreatment composition was prepared by dissolving chloroauric acid (0.1 wt%, based on the total weight of the composition), and ammonium bifluoride (0.006 M) in DI water. A clean piece of chemically pure, grade-1 titanium approximately 1” x 3” with a thickness of 0.004” was treated by submerging the foil in the 0.06 M ammonium bifluoride aqueous treatment solution at pH 2.5 for 2.5 minutes, followed by a rinse with DI water, then immediately followed by submerging in the gold pretreatment composition described above for 2.5 minutes. Afterward, the foil was rinsed with DI water anddried under a stream of air. X-ray fluorescence spectroscopy (XRF) was collected at a 40 kV voltage, 9uA current with a measurement duration of 30 seconds to confirm gold deposition as shown in Figure 19 to confirm gold deposition. The foil was heat treated for 5 days at 250 °C and the ICR growth rate was 0.02 mΩ ^cm2 / h.

[0237] It will be appreciated by skilled artisans that numerous modifications and variations are possible in light of the above disclosure without departing from the broad inventive concepts described and exemplified herein. Accordingly, it is therefore to be understood that the foregoing disclosure is merely illustrative of various exemplary aspects of this application and that numerous modifications and variations can be readily made by skilled artisans which are within the spirit and scope of this application and the accompanying claims.

Claims

What is claimed is:

1. An aqueous treatment composition comprising: more than 0.0% by weight and up to 28% by weight of a fluorometallic acid, based on the total weight of the composition; and a fluoride salt, wherein the fluoride salt is a different component than the fluorometallic acid; wherein the aqueous treatment composition comprises less than 30% by weight nitric acid, based on the total weight of the composition.

2. The aqueous treatment composition of claim 1, wherein the fluorometallic acid is present in an amount up to 5% by weight, based on the total weight of the composition.

3. The aqueous treatment composition of any of the preceding claims, wherein the metal in the fluorometallic acid comprises a Group IIIA metal, a Group IVA metal, a Group IVB metal, and / or a Group VIII metal, and the fluoride in the fluorometallic acid has a mole ratio to the Group IIIA metal, Group IVA metal, Group IVB metal, Group VI metal, and / or Group VIII metal of more than 4.

4. The aqueous treatment composition of any of the preceding claims, wherein the fluorometallic acid comprises hexafluorosilicic acid.

5. The aqueous treatment composition of any of the preceding claims, wherein the fluoride salt comprises ammonium bifluoride.

6. The aqueous treatment composition of any of the preceding claims, wherein the aqueous treatment composition comprises free fluoride in an amount of at least 2 ppm, based on total weight of the pretreatment composition; and total fluoride in an amount of at least 50 ppm, based on total weight of the pretreatment composition.

7. A method of treating a metal substrate comprising contacting at least a portion of the metal substrate with the aqueous treatment composition of any of the preceding claims.

8. The method of claim 7, wherein the metal substrate comprises titanium and / or a titanium alloy.

9. A metal substrate treated according to the method of claim 8.

10. The metal substrate of claim 9, wherein a ratio of the percentage of Ti3+to the percentage of Ti2+of the metal substrate as measured using high resolution X-ray photoelectron spectroscopy is at least 0.

7.

11. The metal substrate of any of claims 9 or 10, wherein the metal substrate has an interfacial contact resistivity of less than 5 mΩ cm2, as measured according to the ICR TEST METHOD 12. The metal substrate of any of claims 9-11, wherein the metal substrate treated with the aqueous treatment composition has a TOF-SIMs depth profile for H+ / Ti+ relative ion intensity inverse peak within 0-5 nm depth of at least 0.002, and / or the metal substrate treated with the aqueous treatment composition has a TOF-SIMs depth profile for Na+ / Ti+relative ion intensity inverse peak within 0.5 nm depth of no more than 3.

2.

13. A pretreatment composition comprising: an acid; a source of a metal comprising vanadium, manganese, nickel, silicon, ruthenium, rhodium, palladium, gold, tin, tantalum, tungsten, iridium, silver, mercury, thallium, lead, bismuth, polonium, platinum, niobium, titanium, cerium, or a combination thereof; a source of free fluoride; and an aqueous medium, wherein the acid, the source of a metal, and the source of free fluoride are each different components.

14. The pretreatment composition of claim 13, wherein the metal comprises niobium, platinum, or gold.

15. The method of any of claims 7-8, wherein the method further comprises contacting at least a portion of the metal substrate with the pretreatment composition of any of the preceding claims 13-14.

16. The method of claim 15, wherein the method further comprises (1) heating the pretreatment composition to a temperature of 30°C to 60°C, and / or (2) stirring the pretreatment composition during contacting the metal substrate with the pretreatment composition.

17. A metal substrate treated according to the method of claim 16.

18. The metal substrate of any of the preceding claims 9-12 or 16, wherein the metal substrate comprises a part of a proton exchange membrane electrolyzer.

19. The metal substrate of any of the preceding claims 9-12 or 16, wherein the metal substrate comprises a part of a composite structure.

20. A kit comprising: the aqueous treatment composition of any of claims 1-6, and / or the pretreatment composition of any of claims 13-14, and optionally instructions for treating a substrate with the aqueous treatment composition, the pretreatment composition, or both the aqueous treatment composition and the pretreatment composition.

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