A process for sealing an aluminum substrate to improve resistance properties

Abstract

A process is described to seal an aluminum or aluminum alloy substrate and improve the alkaline resistance properties of the aluminum or aluminum alloy substrate while providing a favorable appearance. A multi-bath sealing system and kit that includes at least one low temperature bath with a first sealing composition that has at least one nickel ion source and at least one fluoride ion source, and at least one high temperature bath with a second sealing composition that has at least one silicate is also included.

Description

33224-10 (IS)-WO-AA PROCESS FOR SEALING AN ALUMINUM SUBSTRATE TO IMPROVE RESISTANCE PROPERTIESFIELD OF THE INVENTION

[0001] The present invention relates generally to a process of sealing an aluminum substrate and a multi-bath sealing system for use therein.BACKGROUND OF THE INVENTION

[0002] Aluminum substrates are used in the automotive, household, and architectural industries because of their favorable treating conditions and corrosion resistance properties. Aluminum substrates can undergo several different treatments to improve desired properties for various industries. For example, aluminum substrates can be cleaned and then etched with an alkaline substance. After etching, the aluminum substrate undergoes an anodization process, which oxidizes the aluminum substrate to create an anodized aluminum oxide (“AAO”) layer. The AAO layer is porous and colorable for further treatments. The anodization process occurs in a controlled acidic media under several variable parameters including, for example, voltage, current, pH, temperature, acid concentration, agitation, aluminum concentration, and the amount and types of additives.

[0003] After anodization, the porous and colorable AAO layer may, optionally, be electrocolored by an electrolytic coloring process, which occurs when an anodized aluminum substrate is subjected to a set voltage and current (often alternating current) in heavy metal salt solutions. In this process, the heavy metal pigment is deposited into the pores of the AAO layer during the first half cycle of the alternating current. The AAO layer is further thickened by anodic oxidation in the second half cycle of the alternating current. The heavy metal that is deposited at the bottom of the pores in the AAO layer colors the aluminum substrate.

[0004] US5587063A to Kuhm et al., the subject matter of which is herein incorporated by reference in its entirety, describes an electrocoloring process. However, Kuhm fails to describe a method of sealing the porous aluminum substrate after electrocoloring.

[0005] Whether or not the aluminum substrate is subjected to an electrocoloring process, the AAO layer is still porous. Therefore, after the anodization and / or electrolytic coloring processes, the pores of the AAO layer are typically closed in a sealing process, which may include one or more33224-10 (IS)-WO-Aof low, medium, and high temperature sealing baths. Sealing processes impart on the aluminum substrate improved resistance properties, including corrosion, acidic, and / or alkaline resistance. However, in certain industries such as the automotive industry, existing sealing processes are inadequate to improve the resistance properties necessary to meet rigorous industry standards. For example, such sealing processes are inadequate to improve alkaline resistance properties and scratch resistance properties when an aluminum substrate is brought into contact with an alkaline bath at a pH of about 13 (aluminum substrates must undergo similar conditions when exposed to the environment and / or real world conditions).

[0006] EP0193964B1 to Schoener et al., the subject matter of which is incorporated by reference in its entirety, describes an aqueous low temperature bath (no greater than 40°C), with an acidic sealing composition that includes, as essential ingredients, zirconium and / or titanium, fluoride ions, and an additive that is either thiourea, a silicate based on SiCh, or a mixture thereof. However, among other things, the aqueous low temperature bath does not provide the aluminum substrate with adequate alkaline resistance properties.

[0007] US7851025B2 to Lawlor, the subject matter of which is incorporated by reference in its entirety, relates to a method for treating fully sealed anodized aluminum substrates. Lawlor describes an aqueous silicate solution that includes an alkali metal silicate. The aluminum substrate is treated with the silicate solution only after the substrate is fully sealed by some previous method. However, among other things, Lawlor fails to adequately describe a low temperature bath and does not provide the aluminum substrate with sufficient alkaline resistance properties.

[0008] US20120244280A1 to Hecht, the subject matter of which is incorporated by reference in its entirety, describes a multi-step method for producing acidic and alkaline resistant, high-gloss anodized aluminum surfaces. Hecht describe a first sealing composition containing a water-soluble alkali silicate and a second sealing composition with inorganic compounds and fluoride ions. However, among other things, Hecht requires that the inorganic compounds be based on zirconium, titanium, and / or silicates.

[0009] WO2023115366 to Jang et al., the subject matter of which is incorporated by reference in its entirety, describes a sealing composition kit comprising a first sealing composition for use in a medium temperature bath and a second sealing composition for use in a high temperature bath. The first sealing composition requires fluoride ions, a first ion that is nickel, cobalt, chromium, cadmium, and mixtures thereof, and a second ion that is zirconium, titanium, silicon, and mixtures33224-10 (IS)-WO-Athereof. The second sealing composition includes a water-soluble polymer that is poly (meth) acrylic acid and its derivatives, polyether and its derivatives, polyamide and its derivatives, poly (sulfonic acid) and its derivatives, and mixtures thereof. However, Jang also requires that all of sealing baths operate at an elevated temperature.

[0010] EP3245317 to Mangano, describes a sealing process of an aluminum substrate, followed by an additional treatment process with a silicate sealing composition. However, among other things, Mangan describes a low temperature bath that only has nickel fluoride or a higher temperature sealing bath.

[0011] Current technologies may initially pass an alkaline resistance test, but fail the test after a scratch test because they are not scratch resistant. Also, the automotive industry desires a favorable surface appearance, corrosion resistance, and alkaline resistance. Thus, it would be desirable to provide a process for sealing aluminum substrates that at least imparts high alkaline resistance, high scratch resistance, and has a favorable surface appearance.SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide an improved sealing process for aluminum substrates.

[0013] It is another object of the present invention to provide a sealing process that imparts improved alkaline resistance properties to aluminum substrates.

[0014] It is another object of the present invention to provide a sealing process that improves the scratch resistant properties of aluminum substrates.

[0015] It is still another object of the present invention to provide a sealing process that imparts a favorable surface appearance on aluminum substrates.

[0016] It is yet another object of the present invention to provide a multi-bath sealing process that includes at least one low temperature bath and at least one high temperature bath.

[0017] To that end, in one embodiment, the present invention relates generally to a process for sealing an aluminum substrate comprising the steps of:a) bringing the aluminum substrate into contact with an aqueous low temperature bath that comprises a first sealing composition;wherein the first sealing composition comprises at least one nickel ion source and at least one fluoride ion source;33224-10 (IS)-WO-Ab) bringing the aluminum substrate into contact with an aqueous high temperature bath that comprises a second sealing composition;wherein the second sealing composition comprises at least one silicate; and c) optionally, bringing the aluminum substrate into contact with an aqueous aging bath comprising at least one aging component.

[0018] In another embodiment, the present invention also relates generally to a multi-bath sealing system for sealing an anodized aluminum substrate comprising:a) a first bath comprising a first sealing composition that comprises at least one nickel ion source and at least one fluoride ion source;b) a second bath comprising a second sealing composition that comprises at least one silicate; andc) optionally, a third bath comprising at least one aging component.

[0019] In a further embodiment, the present invention relates generally to a multi-part kit for treating an anodized aluminum substrate to form a sealing layer thereon, the kit comprising: a) a first sealing composition comprising at least one nickel ion source and at least one fluoride source;b) a second sealing composition comprising at least one silicate; andc) an aging composition comprising at least one aging component.BRIEF DESCRIPTION OF THE FIGURES

[0020] The accompanying figures, which are incorporated in and constitute a part of this disclosure, depict various implementations of examples and comparative examples in accordance with the present invention and conventional systems, in which:

[0021] Figs. 1A and IB depict four sealed aluminum substrates, wherein Fig. 1A shows the aluminum substrates after a pH 13 alkaline resistance test and Fig. IB shows the aluminum substrates after a scratch test and a pH 13 alkaline resistance test. In Figs. lAand IB, the numbers correspond to (1) Example 1, (2) Comparative Example 1, (3) Comparative Example 2, and (4) Comparative Example 3.

[0022] Fig. 2 depicts sealed aluminum substrates in accordance with the present invention wherein (1) is the present invention after being brought into contact with an aging bath and (2) is the present invention without being brought into contact with an aging bath.33224-10 (IS)-WO-ADETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention relates generally to a process for sealing aluminum substrates and the improved aluminum substrate thereof. Aluminum substrates that are natural (i.e. nonelectrocolored) or electrocolored are brought into contact with a low temperature bath and a high temperature bath. The low temperature bath includes a first sealing composition that includes at least one nickel ion source and at least one fluoride ion source. The high temperature bath includes a second sealing composition that includes at least one silicate, which is preferably a metasilicate. The multi-step process at least imparts strong corrosion, alkaline, and scratch resistant properties. The multi-step process, system, and kit described herein may also provide a favorable appearance.

[0024] As used herein, “a,” “an,” and “the” refer to both singular and plural referents unless the context clearly dictates otherwise.

[0025] As used herein, the term “about” refers to a measurable value such as a parameter, an amount, a temporal duration, and the like and is meant to include variations of + / -15% or less, preferably variations of + / -10% or less, more preferably variations of + / -5% or less, even more preferably variations of + / -1% or less, and still more preferably variations of + / -0.1% or less of and from the particularly recited value, in so far as such variations are appropriate to perform in the invention described herein. Furthermore, it is also to be understood that the value to which the modifier “about” refers is itself specifically disclosed herein.

[0026] As used herein, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, are used for ease of descriptions to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. It is further understood that the terms “front” and “back” are not intended to be limiting and are intended to be interchangeable where appropriate.

[0027] As used herein, the terms “comprises” and / or “comprising” specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0028] As used herein, the term “substantially-free”, if not otherwise defined herein for a particular element or compound, means that a given element or compound is not detectable by ordinary analytical means that are well known to those skilled in the art of metal plating for bath33224-10 (IS)-WO-Aanalysis. Such methods typically include atomic absorption spectrometry, titration, UV-Vis analysis, secondary ion mass spectrometry, and other commonly available analytical methods.

[0029] As used herein, the terms “aluminum substrate” and “aluminum alloy substrate” can be used interchangeably and mean a substrate that comprises aluminum and / or an aluminum alloy.

[0030] As used herein, the term “low temperature” means a solution, bath, system, electrolyte, composition, and / or apparatus that is maintained at a temperature in the range of about 15 to about 45°C.

[0031] As used herein, the term “medium temperature” means a solution, bath, system, electrolyte, composition, and / or apparatus that is maintained at a temperature in the range of about 45 to about 70°C.

[0032] As used herein, the term “high temperature” means a solution, bath, system, electrolyte, composition, and / or apparatus that is maintained at a temperature in the range of about 70 to about 100°C.

[0033] In one embodiment, the present invention relates generally to a process for sealing an aluminum substrate comprising the steps of:a) bringing the aluminum substrate into contact with an aqueous low temperature bath that comprises a first sealing composition;wherein the first sealing composition comprises at least one nickel ion source and at least one fluoride ion source;b) bringing the aluminum substrate into contact with an aqueous high temperature bath that comprises a second sealing composition;wherein the second sealing composition comprises at least one silicate; and c) optionally, bringing the aluminum substrate into contact with an aqueous aging bath comprising at least one aging component.

[0034] The step of bringing the aluminum substrate into contact with any aqueous bath can be accomplished through various means known by those skilled in the art including, for example, spraying, immersing, coating, washing, and / or otherwise engaging the aluminum substrate with the aqueous baths.

[0035] In embodiments, the aluminum substrate is an anodized aluminum substrate. After the anodized aluminum substrate is treated in at least the low temperature bath and / or the high temperature bath, the substrate is a sealed aluminum substrate. In a preferred embodiment, the33224-10 (IS)-WO-Asteps described in the above process occur in sequential order. That is, the (anodized) aluminum substrate is first brought into contact with the low temperature bath and subsequently brought into contact with the high temperature bath. The sealed aluminum substrate may optionally be brought into contract with the aging bath after the high temperature bath.

[0036] The aluminum substrate may include aluminum metal and / or an aluminum alloy. When an aluminum alloy is present, the aluminum content may be at least about 70 wt.%, preferably at least about 80 wt.%, more preferably at least about 90 wt.%, even more preferably at least about 95 wt.%, more preferably at least about 98 wt.%, even more preferably at least about 99 wt.%. With reference to The Aluminum Association (2022) ANSI / AA designation system for wrought alloys, the aluminum alloy can include, but is not limited to, the compositions shown below in Table 1 :TABLE 1> >>> >>>

[0037] Specific examples of aluminum alloys include, but are not limited to, AA2024, AA5754, AA6060, AA6061, AA6063, AA6082, AA6463, and AA7075.

[0038] Turning to the first sealing composition, the at least one nickel ion source may be selected from the group consisting of nickel sulfate, nickel sulfamate, nickel acetate, nickel nitrate, nickel carbonate, nickel fluoride, and combinations of one or more of the foregoing. In one embodiment, the at least one nickel ion source includes nickel sulfate. In a preferred embodiment, the nickel ion source is provided as a nickel-based aqueous solution. The concentration of nickel ions in the nickel-based aqueous solution can be in the range of about 0.5 to about 5.0 g / L, preferably about 0.8 to about 2.5 g / L, more preferably about 1 to about 2 g / L. The total concentration of nickel ions33224-10 (IS)-WO-Ain the first sealing composition is in the range of about 0.3 to about 4.0 g / L, preferably about 0.5 to about 2.0 g / L, more preferably about 0.8 to about 1.8 g / L.

[0039] The at least one fluoride ion source may be selected from the group consisting of potassium fluoride, potassium bifluoride, hydrogen fluoride, sodium fluoride, sodium bifluoride, ammonium fluoride, ammonium bifluoride, nickel fluoride, a heavy metal fluoride complex, and combinations of one or more of the foregoing. In a preferred embodiment, the at least one fluoride ion source comprises nickel fluoride and at least one additional fluoride ion source. In one embodiment, the at least one fluoride ion source includes potassium fluoride. In a preferred embodiment, the fluoride ion source is provided as a fluorine-based aqueous solution. The concentration of fluoride ions in the fluorine-based aqueous solution can be in the range of about 100 to about 1500 ppm, preferably about 150 to about 1000 ppm, more preferably about 400 to about 800 ppm. The total concentration of fluoride ions in the first sealing composition is in the range of about 200 to about 1000 ppm, preferably about 400 to about 800 ppm, more preferably about 500 to about 700 ppm.

[0040] The fluorine-based aqueous solution may optionally include a carbonate salt component. The carbonate salt may be selected from the group consisting of calcium carbonate, potassium carbonate, magnesium carbonate, sodium carbonate, lithium carbonate, barium carbonate, and combinations of one or more of the foregoing. In one embodiment, the carbonate salt includes calcium carbonate. The concentration of the carbonate salt in the fluorine-based aqueous solution can be in the range of about 0 to about 3.0 g / L, preferably about 0.5 to about 2.5 g / L, more preferably about 1 to about 2 g / L.

[0041] As described herein, the separate addition (i.e. distinct components) of the at least one nickel ion source and the at least one fluoride ion source unexpectedly yields better results than a nickel and fluoride ion source as a single component (i.e. nickel fluoride). In one embodiment, the at least one nickel ion source and the at least one fluoride ion source are added to the bath separately from distinct component sources. Based thereon, in a preferred embodiment, the first sealing composition comprises at least one fluoride ion source is at least substantially free of nickel such that the nickel ion source and the fluoride ion source constitute separate additions to the first sealing composition. In embodiments, the at least one nickel ion source comprises nickel fluoride and the at least one fluoride ion source comprises a different fluoride compound.

[0042] As described herein, the low temperature bath is maintained at a pH in the range of about 5.0 to about 7.0, preferably about 5.5 to about 6.5, more preferably about 5.7 to about 6.3. The low33224-10 (IS)-WO-Atemperature bath is further maintained at a temperature in the range of about 15 to about 45 °C, preferably about 20 to about 35°C, more preferably about 25 to about 30°C. In embodiments, the low temperature bath applies the first sealing composition to the aluminum substrate at a rate in the range of about 0.5 to about 1.6 min / pm, preferably about 0.75 to about 1.4 min / pm, more preferably about 0.9 to about 1.3 min / pm. The low temperature seal has a thickness in the range of about 3 to about 30 pm, preferably about 9 to about 20 pm, more preferably about 12 to about 18 pm.

[0043] After the first sealing composition is applied, the aluminum substrate is brought into contact with a high temperature bath. The high temperature bath includes a second sealing composition that includes at least one silicate. The silicate may be selected from the group consisting of sodium silicate, potassium silicate, magnesium silicate, calcium silicate, and combinations of one or more of the foregoing. In one embodiment, the silicate is sodium silicate and / or potassium silicate. The silicate is preferably a metasilicate of the above listed compounds. In one embodiment, the metasilicate is sodium and / or potassium metasilicate. In a preferred embodiment, the silicate is added to the high temperature bath as an aqueous solution with a concentration of silicate (SiCh) in the range of about 0.2 to about 3.0 g / L, preferably about 0.37 to about 1.5g / L, more preferably about 0.49 to about 0.74 g / L. The concentration of total silicate present in the high temperature bath is in the range of about 0.2 to about 3.5g / L, preferably about 0.3 to about 1.5 g / L, more preferably about 0.5 to about 1.0 g / L.

[0044] As described herein, the high temperature bath is maintained at a pH in the range of about 7.0 to about 12.0, preferably about 8.0 to about 11.0, more preferably about 8.5 to about 10.0. The high temperature bath is further maintained at a temperature in the range of about 70 to about 100°C, preferably about 75 to about 95°C, more preferably about 80 to about 90°C. In one embodiment, the high temperature bath applies the second sealing composition at a rate in the range of about 1.5 to about 4 min / pm, preferably about 2 to about 3.5 min / pm, more preferably about 2.5 to about 3 min / pm. The high temperature seal has a thickness in the range of about 3 to about 30 pm, preferably about 9 to about 20 pm, more preferably about 12 to about 18 pm.

[0045] The aluminum substrate may further be rinsed before or after any step in the process. Example process steps include cleaning, etching, anodizing, electrocoloring, low temperature sealing, high temperature sealing, and / or aging. That is, the aluminum substrate may be rinsed before or after any and / or all of the above processes.33224-10 (IS)-WO-A

[0046] Optionally, after the aluminum substrate is brought into contact with the sealing baths, the aluminum substrate may optionally be brought into contact with a third sealing bath. The third sealing bath is an aging bath that includes at least one aging component to improve the surface appearance of the aluminum substrate. In one embodiment, the aging component is selected from the group consisting of propenoic acid, a polycarboxylate copolymer, phosphino carboxylic acid, and combinations of one or more of the foregoing. In one embodiment, the concentration of the aging component in the aging bath is in the range of about 0.01 to about 4 g / L, preferably about 0.5 to about 3 g / L, more preferably about 1 to about 2 g / L. The aluminum substrate may also be brought into contact with the aging bath prior to contact with the low and / or high temperature sealing baths, if desired.

[0047] As described herein, the aging bath is maintained at a pH in the range of about 5.0 to about 7.0, preferably about 5.4 to about 6.4, more preferably about 5.7 to about 6.1. The aging bath is further maintained at a temperature in the range of about 60 to about 100 °C, preferably about 70 to about 100°C, more preferably about 80 to about 100°C, even more preferably about 90 to about 100°C. In embodiments, the aluminum substrate is brought into contact with the aging bath for period of time in the range of about 2 to about 10 minutes, preferably about 3 to about 8 minutes, more preferably about 4 to about 6 minutes.

[0048] The necessary favorable surface appearance of the aluminum substrate can be quantified using an Energy Dispersive X-ray (EDX) analysis. A suitable EDX spectroscopy microscope is the Axia ChemiSEM, available from Thermo Fisher Scientific (Waltham, MA). The EDX analysis quantifies the chemical composition of the AAO layer. In one embodiment, the EDX analysis evaluated a favorable surface appearance of the aluminum substrate based on the presence of fluorine, oxygen, silicon, and nickel. The ratio of fluoride to oxygen on the surface of the aluminum substrate is in the range of about 0.03: 1 to about 2:1, the amount of silicon on the surface of the aluminum substrate is in the range of about 0.3 to about 2.0 wt.%, and the ratio of nickel to silicon on the surface of the aluminum is in the range of about 0.7:1 to about 3:1.

[0049] Prior to the process of sealing the AAO layer, the aluminum substrate may be subjected to multiple pretreatment processes. These treatment processes include, but are not limited to, cleaning, alkaline etching, anodizing, and electrocoloring. Electrocoloring includes the use of heavy metals and electric currents to fill the exposed pores of the AAO layer from the anodization process. The heavy metals used are typically elements of the first transition series, including33224-10 (IS)-WO-Achromium, manganese, iron, cobalt, nickel, copper, and, in particular, tin. Heavy metal salts are generally used as sulfates, with a pH value of about 0.1 to about 2.0, and the pH of the electrocoloring baths are adjusted and maintained with sulfuric acid. The coloring process is carried out at a voltage of about 10 to about 25 V and the resulting current density. The aluminum substrate acts as the cathode and the counter-electrode may either consist of graphite or stainless steel or the same material that is dissolved in the electrocoloring electrolyte.

[0050] One example of a sequence of multiple pretreatment options is disclosed in Afsin, Pinar. et al., Electro-Coloring Mechanism of Aluminum Anodic Oxides in Tin-Based Electrolytes, 14 Coatings 616 (2024), which is expressly incorporated herein by reference. An aluminum alloy substrate is etched in an alkaline sodium hydroxide solution (2.5 M solution of NaOH, 60°C, 3 min) and followed by 2 M of nitric-acid-based neutralization for 3 min. After neutralization the aluminum substrate is anodized by applying 16V Direct Current at 19°C in a 1.7 M H2SO4 aqueous solution in a conventional two-electrode cell with an aluminum counter electrode. The resulting thickness of the aluminum anodic oxide (AAO) layers are 11 ± 1 pm. Once anodized, the aluminum substrate is electrocolored in a bath that includes 0.1 M SnSO4, 0.2 M H2SO4, and 0.05 M sulfosalicylic acid as a stabilizer at 17 V (alternating current-50 Hz) at 24°C.

[0051] After the aluminum substrate is colored, the pores are closed using the sealing process of the present invention to improve the surface appearance, acidic, alkaline, and / or corrosion resistance.

[0052] The present invention will now be illustrated with reference to the following non-limiting examples:

[0053] Pretreatment of the aluminum substrate:

[0054] For all examples and comparative examples, the aluminum substrate is Aluminum Alloy 6063. That is the aluminum substrate has the general composition of 98.9 wt.% Al, 0.7 wt.% Mg, 0.4 wt.% Si, and minor impurities. The aluminum substrate is subjected to the following steps:1) Pretreatment with a cleaner comprising 50 g / L Alumal Clean at 65°C for 10 minutes; 2) Alkaline etch comprising Alumal Etch 235 and 65 g / L NaOH at 65°C for 6 minutes; 3) Anodization in 24 g / L Alumal Elox 557 and 170 g / L H2SO4 for 15 pm; and4) Electrocoloration in 70 g / L Alumal Color 890, 25 g / L Alumal Color 891, and 16 g / LH2SO4 at 25°C for 7 minutes.33224-10 (IS)-WO-A

[0055] All of the above Alumal compounds are available from MacDermid Enthone (West Haven, CT). It can be appreciated to one skilled in the art that other pre-treatment processes and ordering of treatment options may be used without departing from the scope of the present invention.

[0056] The sealing compositions and conditions according to Examples 1 and 2 are provided below in Table 2:TABLE 2

[0057] To make the first sealing composition of Examples 1 and 2, 18 g of Ni-based aqueous solution stock solution and 5 g KF and calcium carbonate based aqueous solution stock solution is dissolved in 1 L of deionized water.

[0058] While the present samples include a carbonate salt with the at least one fluoride ion source, one of skill in the art may apply the cold seal on the aluminum substrate without a carbonate salt component. To make the first sealing composition without a carbonate component, 18 g of Ni-based aqueous stock solution and 3.5 g of ammonium bifluoride based aqueous stock solution is dissolved in 1 liter of deionized water. Then, pH is maintained at 6.1.

[0059] To make the second sealing composition of Examples 1 and 2, 25 g of sodium silicon-based hot seal stock solution is dissolved in IL of deionized water. Then, pH is maintained at 8.9. While the present examples include sodium silicate, one of skill in the art may use a silicon-based hot seal provided with 25 g of potassium Si-based hot seal stock solution is dissolved in 1 liter of deionized water.

[0060] To make the aging bath of Example 2, 1.5 g of propenoic acid stock solution is dissolved in 1 L of deionized water. Then, pH is maintained at 5.9.33224-10 (IS)-WO-A

[0061] After the aqueous bath with the sealing compositions are made, the aluminum substrate is brought into contact with the bath containing Sealing Composition 1. After a desired amount of time, the aluminum substrate is brought into contact with the bath containing Sealing Composition 2. Last, in accordance with Example 2, the aluminum substrate is brought into contact with the aging bath containing Sealing Composition 3.

[0062] The sealing compositions and conditions according to Comparative Examples 1-4 are provided below in Table 3:TABLE 3

[0063] After each sealing bath was constructed according to comparative examples, the aluminum substrate was brought into contact with the bath containing Sealing Composition 1. Next, after the desired period of time, the aluminum substrate is brought into contact with the bath containing Sealing Composition 2 (if applicable).

[0064] Testing Conditions:

[0065] After the aluminum substrates were sealed according to the examples and comparative examples below, the aluminum substrates were subjected to an alkalinity resistance test. The test is performed by bringing the aluminum substrate into contact with a bath with a pH of 13 for 10 minutes. The amount of resistance is measured by evaluating the change in color of the aluminum substrates. The degree of color change is measured according to the AATCC Evaluation 133224-10 (IS)-WO-AProcedure (IS0105-A02) testing standard (Edition 4, 2005), which is expressly incorporated herein by reference. Two sets of aluminum substrates were tested for the change in color: (1) after an alkalinity resistance test and (2) after the aluminum substrates were subjected to a scratch test and subsequently an alkalinity resistance test.

[0066] As shown in (1) of Figs. lAand IB, the sealing process according to Example 1 provided a scratch and alkaline resistant aluminum substrate under both tests. There was no change in color under the IS0105-A02 standard, indicating that the aluminum substrate passed the test. As shown in Fig. 2, the additional step of bringing the aluminum substrate into contact with an aging bath (2) did not affect the color and still passed the test while improving the surface appearance.

[0067] By contrast, Comparative Examples 1-4 failed both tests. Each comparative test was based on prior sealing processes to demonstrate that prior systems cannot provide adequate alkaline and scratch resistance on an aluminum substrate. The corresponding systems are shown below:• Comparative Example 1: EP0193964• Comparative Example 2: US7851025• Comparative Example 3: WO2023115366• Comparative Example 4: US20120244280

[0068] In every single example, as shown by (2)-(4) of Figs. 1A and IB, there was a noticeable color change in the aluminum substrate. This means that the aluminum substrates of these prior methods did not provide adequate scratch resistant or alkaline resistant properties that the present invention achieved. The color change both before and after the scratch test demonstrates that these sealing processes are ineffective when exposed to real world conditions and the rigorous testing standings in various industries.

[0069] Finally, it should also be understood that while the present invention has been described and illustrated by reference to particular embodiment, the claims are intended to cover all of the generic and specific features of the invention described herein and all statements of the scope of the invention that as a matter of language might fall there between.ADDITIONAL EMBODIMENTSClause 1: A process for sealing an aluminum substrate comprising the steps of:a) bringing the aluminum substrate into contact with an aqueous low temperature bath that comprises a first sealing composition;33224-10 (IS)-WO-Awherein the first sealing composition comprises at least one nickel ion source and at least one fluoride ion source;b) bringing the aluminum substrate into contact with an aqueous high temperature bath that comprises a second sealing composition;wherein the second sealing composition comprises at least one silicate; and c) optionally, bringing the aluminum substrate into contact with an aqueous aging bath comprising at least one aging component.Clause 2: The process according to Clause 1, wherein steps a)-c) occur in sequential order.Clause 3: The process according to Clauses 1 or 2, wherein the aluminum substrate is an anodized aluminum substrate.Clause 4: The process according to any of the preceding Clauses, wherein the aluminum substrate is electrocolored prior to bringing the aluminum substrate into contact with the aqueous low temperature bath.Clause 5: The process according to any of the preceding Clauses, wherein the aluminum substrate comprises an aluminum alloy, wherein the aluminum alloy has an aluminum content of at least about 90 wt.%, preferably wherein the aluminum content is at least about 95 wt.%.Clause 6: The process according to any of the preceding Clauses, wherein the at least one nickel ion source is selected from the group consisting of nickel sulfate, nickel sulfamate, nickel acetate, nickel nitrate, nickel carbonate, nickel fluoride, and combinations of one or more of the foregoing.Clause 7: The process according to any of the preceding Clauses, wherein the at least one nickel ion source comprises a nickel-based aqueous solution, optionally wherein the concentration of nickel ions in the nickel-based aqueous solution is in the range of about 0.5 to about 5.0 g / L. Clause 8: The process according to any of the preceding Clauses, wherein the at least one fluoride ion source is selected form the group consisting of potassium fluoride, potassium bifluoride, hydrogen fluoride, sodium fluoride, sodium bifluoride, ammonium fluoride, ammonium bifluoride, nickel fluoride, a heavy metal fluoride complex, and combinations of one or more of the foregoing.Clause 9: The process according to Clause 8, wherein the at least one source of fluoride ions comprises a fluorine-based aqueous solution, optionally wherein the concentration of fluoride ions in the fluorine-based aqueous solution is in the range of about 100 to about 1500 ppm.33224-10 (IS)-WO-AClause 10: The process according to Clause 9, wherein the fluorine-based aqueous solution further comprises at least one carbonate salt, optionally wherein the at least carbonate salt is selected from the group consisting of calcium carbonate, potassium carbonate, magnesium carbonate, sodium carbonate, lithium carbonate, barium carbonate, and combinations of one or more of the foregoing.Clause 11: The process according to any of the preceding Clauses, wherein the at least one nickel ion source and the at least one fluoride ion source are added to the low temperature bath separately as distinct sealing composition components, optionally, wherein the at least one fluoride ion source is at least substantially free of nickel such that the at least one nickel ion source and the at least one fluoride ion source constitute separate additions to the aqueous low temperature bath.Clause 12: The process according to any of the preceding Clauses, wherein the aqueous low temperature bath is maintained at a temperature in the range of about 15 to about 45°C and / or wherein the aqueous low temperature bath creates a seal on the aluminum substrate at a rate in the range of about 0.5 to about 1.6 min / pm and / or wherein the low temperature bath creates a seal on the aluminum substrate that has a thickness in the range of about 3 to about 30 pm and / or wherein the aqueous low temperature bath is maintained at a pH in the range of about 5 to about 7.Clause 13: The process according to any of the preceding Clauses, wherein the at least one silicate is selected from the group consisting of sodium silicate, potassium silicate, magnesium silicate, calcium silicate, and combinations of one or more of the foregoing optionally, wherein the at least one silicate is a metasilicate.Clause 14: The process according to any of the preceding Clauses, wherein the at least one silicate comprises a silicon-based aqueous solution optionally, wherein the concentration of silicate in the silicon-based aqueous solution is in the range of about 0.2 to about 3.0 g / L.Clause 15: The process according to any of the preceding Clauses, wherein the aqueous high temperature bath is maintained at a temperature in the range of about 70 to about 100°C and / or wherein the aqueous high temperature bath creates a seal on the aluminum substrate at a rate in the range of about 1.5 to about 4 min / pm and / or wherein the high temperature bath creates a seal on the aluminum substate that has a thickness in the range of about 3 to about 30 pm and / or wherein the aqueous high temperature bath is maintained at a pH in the range of about 7 to about 12.33224-10 (IS)-WO-AClause 16: The process according to any of the preceding Clauses, wherein the aging component is selected from the group consisting of propenoic acid, polycarboxylate copolymer, phosphino carboxylic acid, and combinations of one or more of the foregoing.Clause 17: The process according to any of the preceding Clauses, wherein the concentration of the aging component in the aging bath is in the range of about 0.01 to about 4 g / L and / or wherein the aging bath is maintained at a temperature in the range of about 60 to about 100°C and / or wherein the aluminum substrate is brought into contact with the aging bath for a period of time in the range of about 2 to about 10 minutes and / or wherein the aging bath is maintained at a pH in the range of about 5 to about 7.Clause 18: A multi-bath system for sealing an anodized aluminum substrate comprising:a) a first bath comprising a first sealing composition that comprises at least one nickel ion source and at least one fluoride ion source;b) a second bath comprising a second sealing composition that comprises at least one silicate; andc) optionally, a third bath comprising at least one aging component.Clause 19: The system according to Clause 18, wherein the at least one nickel ion source and the at least one fluoride ion source are added to the first bath separately as distinct sealing composition components.Clause 20: The system according to Clauses 18 or 19, wherein the at least one nickel ion source is selected from the group consisting of nickel sulfate, nickel sulfamate, nickel acetate, nickel nitrate, nickel carbonate, nickel fluoride, and combinations of one or more of the foregoing.Clause 21: The system according to any of Clauses 18-20, wherein the first bath is maintained at a temperature in the range of about 15 to about 45°C and / or wherein the second bath is maintained at a temperature in the range of about 70 to about 100°C.Clause 22: A multi-part kit for treating an anodized aluminum substrate to form a sealing layer thereon, the kit comprising:a) a first sealing composition comprising at least one nickel ion source and at least one fluoride source;b) a second sealing composition comprising at least one silicate; andc) an aging composition comprising at least one aging component.33224-10 (IS)-WO-AClause 23: The multi-part according to Clause 22, wherein the at least one nickel ion source and the at least one fluoride ion source are added to the first sealing composition separately as distinct components.

Claims

33224-10 (IS)-WO-AWHAT IS CLAIMED IS:

1. A process for sealing an aluminum substrate comprising the steps of:a) bringing the aluminum substrate into contact with an aqueous low temperature bath that comprises a first sealing composition;wherein the first sealing composition comprises at least one nickel ion source and at least one fluoride ion source;b) bringing the aluminum substrate into contact with an aqueous high temperature bath that comprises a second sealing composition;wherein the second sealing composition comprises at least one silicate; and c) optionally, bringing the aluminum substrate into contact with an aqueous aging bath comprising at least one aging component.

2. The process according to claim 1, wherein steps a)-c) occur in sequential order.

3. The process according to claim 2, wherein the aluminum substrate is electrocolored prior to bringing the aluminum substrate into contact with the aqueous low temperature bath.

4. The process according to claim 1, wherein the aluminum substrate is an anodized aluminum substrate.

5. The process according to claim 1 , wherein the aluminum substrate comprises an aluminum alloy, wherein the aluminum alloy has an aluminum content of at least about 90 wt.%.

6. The process according to claim 5, wherein the aluminum content is at least about 95 wt.%.

7. The process according to claim 1, wherein the at least one nickel ion source is selected from the group consisting of nickel sulfate, nickel sulfamate, nickel acetate, nickel nitrate, nickel carbonate, nickel fluoride, and combinations of one or more of the foregoing.33224-10 (IS)-WO-A8. The process according to claim 1, wherein the at least one nickel ion source comprises a nickel-based aqueous solution.

9. The process according to claim 8, wherein the concentration of nickel ions in the nickel- based aqueous solution is in the range of about 0.5 to about 5.0 g / L.

10. The process according to claim 1, wherein the at least one fluoride ion source is selected form the group consisting of potassium fluoride, potassium bifluoride, hydrogen fluoride, sodium fluoride, sodium bifluoride, ammonium fluoride, ammonium bifluoride, nickel fluoride, a heavy metal fluoride complex, and combinations of one or more of the foregoing.

11. The process according to claim 1 , wherein the at least one source of fluoride ions comprises a fluorine-based aqueous solution.

12. The process according to claim 11, wherein the concentration of fluoride ions in the fluorine-based aqueous solution is in the range of about 100 to about 1500 ppm.

13. The process according to claim 11, wherein the fluorine-based aqueous solution further comprises at least one carbonate salt.

14. The process according to claim 13, wherein the at least carbonate salt is selected from the group consisting of calcium carbonate, potassium carbonate, magnesium carbonate, sodium carbonate, lithium carbonate, barium carbonate, and combinations of one or more of the foregoing.

15. The process according to claim 1 , wherein the at least one nickel ion source and the at least one fluoride ion source are added to the low temperature bath separately as distinct sealing composition components.33224-10 (IS)-WO-A16. The process according to claim 15, wherein the at least one fluoride ion source is at least substantially free of nickel such that the at least one nickel ion source and the at least one fluoride ion source constitute separate additions to the aqueous low temperature bath.

17. The process according to claim 1, wherein the aqueous low temperature bath is maintained at a temperature in the range of about 15 to about 45°C.

18. The process according to claim 1, wherein the aqueous low temperature bath creates a seal on the aluminum substrate at a rate in the range of about 0.5 to about 1.6 min / pm.

19. The process according to claim 1, wherein the low temperature bath creates a seal on the aluminum substrate that has a thickness in the range of about 3 to about 30 pm.

20. The process according to claim 1 , wherein the aqueous low temperature bath is maintained at a pH in the range of about 5 to about 7.

21. The process according to claim 1, wherein the at least one silicate is selected from the group consisting of sodium silicate, potassium silicate, magnesium silicate, calcium silicate, and combinations of one or more of the foregoing.

22. The process according to claim 1, wherein the at least one silicate is a metasilicate.

23. The process according to claim 1, wherein the at least one silicate comprises a silicon- based aqueous solution.

24. The process according to claim 23, wherein the concentration of silicate in the silicon- based aqueous solution is in the range of about 0.2 to about 3.0 g / L.

25. The process according to claim 1, wherein the aqueous high temperature bath is maintained at a temperature in the range of about 70 to about 100°C.33224-10 (IS)-WO-A26. The process according to claim 1, wherein the aqueous high temperature bath creates a seal on the aluminum substrate at a rate in the range of about 1.5 to about 4 min / pm.

27. The process according to claim 1, wherein the high temperature bath creates a seal on the aluminum substate that has a thickness in the range of about 3 to about 30 pm.

28. The process according to claim 1, wherein the aqueous high temperature bath is maintained at a pH in the range of about 7 to about 12.

29. The process according to claim 1, wherein the aging component is selected from the group consisting of propenoic acid, polycarboxylate copolymer, phosphino carboxylic acid, and combinations of one or more of the foregoing.

30. The process according to claim 1, wherein the concentration of the aging component in the aging bath is in the range of about 0.01 to about 4 g / L.

31. The process according to claim 1 , wherein the aging bath is maintained at a temperature in the range of about 60 to about 100°C.

32. The process according to claim 1, wherein the aluminum substrate is brought into contact with the aging bath for a period of time in the range of about 2 to about 10 minutes.

33. The process according to claim 1, wherein the aging bath is maintained at a pH in the range of about 5 to about 7.

34. A multi-bath system for sealing an anodized aluminum substrate comprising:d) a first bath comprising a first sealing composition that comprises at least one nickel ion source and at least one fluoride ion source;e) a second bath comprising a second sealing composition that comprises at least one silicate; and33224-10 (IS)-WO-Af) optionally, a third bath comprising at least one aging component.

35. The system according to claim 34, wherein the at least one nickel ion source and the at least one fluoride ion source are added to the first bath separately as distinct sealing composition components.

36. The system according to claim 34, wherein the at least one nickel ion source is selected from the group consisting of nickel sulfate, nickel sulfamate, nickel acetate, nickel nitrate, nickel carbonate, nickel fluoride, and combinations of one or more of the foregoing.

37. The system according to claim 34, wherein the first bath is maintained at a temperature in the range of about 15 to about 45°C.

38. The system according to claim 34, wherein the second bath is maintained at a temperature in the range of about 70 to about 100°C.

39. A multi-part kit for treating an anodized aluminum substrate to form a sealing layer thereon, the kit comprising:d) a first sealing composition comprising at least one nickel ion source and at least one fluoride source;e) a second sealing composition comprising at least one silicate; andf) an aging composition comprising at least one aging component.

40. The multi-part according to claim 39, wherein the at least one nickel ion source and the at least one fluoride ion source are added to the first sealing composition separately as distinct components.

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