Inorganic non-chromium aqueous treatment composition and method for coating metal surfaces

Abstract

A chromium-free aqueous treatment solution for coating metal surfaces that meets the corrosion resistance, electrical contact resistance, and paint adhesion requirements set forth in MIL-DTL-81706B, Class 3. The treatment solution contains a compound of a Group IV-B element and vanadium ions. The solution can be inorganic and molybdate-free. In one embodiment, the inorganic chromium-free, molybdate-free aqueous treatment solution includes water, a compound of a Group IV-B element, vanadium ions, and optionally a stabilizer, and the composition has a pH greater than or equal to 3.

Description

[Technical Field]

[0001] Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 525,395, filed June 27, 2017, and U.S. Non-Provisional Patent Application No. 16 / 014,045, filed June 21, 2018, the contents of which are incorporated herein by reference.

[0002] Technical Field The present invention relates generally to chromium-free aqueous treatment solutions for coating metal surfaces, and more particularly to inorganic solutions that do not contain molybdate ions. [Background technology]

[0003] Background of the Invention Metals can be corroded by corrosive agents present in the environment in which they operate. For example, an aluminum article operating in a salt-containing environment can have its surface corroded either generally over a large area or locally in a limited area, such as at a weld joint, a bolt hole, or a small inclusion or pit within the surface. Corrosion damage increases over time and with continued exposure to salt. It is believed that such corrosion can lead to premature failure of the article.

[0004] Coatings are widely used to protect surfaces from such corrosion damage. Until now, chromium-containing passivation layers have been primarily used to prevent corrosion of metallic materials, particularly hexavalent chromium. While conversion coating techniques using hexavalent chromium have provided satisfactory results, hexavalent chromium is toxic to the environment and is a designated carcinogen. In an attempt to mitigate the societal risks associated with hexavalent chromium, the use of less toxic trivalent chromate conversion coatings has been adopted.

[0005] However, trivalent chromium is not without risks. During passivation of metal articles with trivalent chromate conversion coatings, there is the possibility of cross-contamination with hexavalent chromium and / or interconversion of trivalent chromium, e.g., by air oxidation of residual trivalent chromium. Therefore, despite the replacement of trivalent chromium in chromate conversion coating processes, the presence of toxic hexavalent chromium may still continue.

[0006] These shortcomings of chromium-based passivation layers have led to intensive efforts to develop chromium-free corrosion inhibitors. For example, the present applicant has commercialized products that successfully improve the corrosion resistance and paint adhesion of metal surfaces. Examples of such compositions are disclosed in U.S. Patent No. 5,859,106 to Jones et al. and U.S. Patent No. 8,728,251 to Greber. Both are directed to aqueous compositions containing a polymer system with carboxylic acid and hydroxyl functional groups and a compound of a Group IV-B element. Both contain organic compounds and molybdate ions, which increase the cost and complexity of product disposal.

[0007] Molybdate ions are nontoxic and less aggressive oxidizers than chromate toward organic additives that may be used in corrosion-inhibiting formulations. A primary application is in the coolant of air-conditioning and heating systems to protect the mild steel used in their construction. Molybdates are used to inhibit corrosion in water-based hydraulic systems and automotive engine antifreeze. Molybdates prevent corrosion due to their ability to be adsorbed by metal oxide layers, filling gaps and thus promoting the formation of an adherent oxide layer. Corrosion of the underlying substrate is prevented as it becomes passive.

[0008] The search for a passivation layer is further complicated by the fact that the passivation layer must be colored. Color is required to allow operators to quickly, easily, and visually inspect the product in industrial applications. Such visual inspection allows for the evaluation of coating quality without expensive testing methods.

[0009] In an effort to standardize the evaluation of various passivation layers for government procurement purposes, the U.S. Department of Defense has published specifications outlining the requirements that must be met for any composition if a supplier intends to sell its product to the government or that must be part of any government contract. MIL-DTL-81706B provides the standards that must be met when coating aluminum surfaces (i.e., aircraft parts). Failure to meet the corrosion resistance, electrical contact resistance, and paint adhesion requirements set forth in MIL-DTL-81706B limits the potential market for the coating, as certain non-government purchasers will also begin to seek coatings that meet the requirements set forth in MIL-DTL-81706B. Therefore, there is a need for a low-cost, chromium-free coating composition for coating metal surfaces that provides sufficient protection to meet the requirements of MIL-DTL-81706B and also produces a visually verifiable color on the metal surface. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 5,859,106 [Patent Document 2] U.S. Patent No. 8,728,251 Summary of the Invention [Means for solving the problem]

[0011] Brief summary of the invention To meet these and other needs and in view of its objectives, a low-cost, chromium-free, aqueous treatment solution for coating metal surfaces is provided. The solution provides sufficient protection to meet the requirements of MIL-DTL-81706B, Class 3, and further produces a visually verifiable color on the metal surface. The composition of the present invention can be used to passivate the surface of the metal surface, improve paint adhesion, and / or improve corrosion resistance. The composition can be used as a paint pretreatment for certain metals, including copper, brass, magnesium, aluminum, and iron alloys.

[0012] In one embodiment, the inorganic chromium-free, molybdate-free aqueous treatment solution comprises water, a compound of a Group IV-B element, vanadium ions, and optionally a stabilizer, wherein the composition has a pH greater than or equal to 3.

[0013] In another embodiment, the present invention encompasses a method for treating a metal surface by contacting the metal surface with an inorganic chromium-free, molybdate-free aqueous treatment composition comprising water, a Group IV-B element compound, and vanadium ions. The method may further include cleaning and rinsing the metal surface with an aqueous silica-containing detergent prior to the initial contacting step. The method may further include rinsing the metal surface with water after contacting the metal surface with the pretreatment composition, and then painting the metal surface.

[0014] The method may further include cleaning and rinsing the metal surface with an aqueous silica-containing cleaner prior to the initial contacting step. The method may further include rinsing the metal surface with water after contacting the metal surface with the pretreatment composition, and then painting the metal surface. Regarding the pH of the aqueous pretreatment composition containing water, a compound of a Group IV-B element, vanadium ions, and optionally a stabilizer, the composition in some embodiments has a pH greater than or equal to 3. DETAILED DESCRIPTION OF THE INVENTION

[0015] Detailed Description of the Invention As used herein, the term "pretreatment composition" refers to any composition that improves paint adhesion and corrosion resistance of a metal surface. Aqueous pretreatment compositions may be used as pretreatments before painting and as passivation solutions to reduce corrosion formation in the uncoated (unpainted) state. Thus, while a composition may be conveniently referred to as a pretreatment composition, it is a composition used for pretreatment (i.e., to improve adhesion of a subsequently applied paint) and passivation (i.e., to resist corrosion of the unpainted surface).

[0016] As used herein, the term "treating" refers to applying a treatment solution, cleaning, rinsing, and applying a pretreatment solution. The pretreatment solution also functions as a sealant to seal the metal surface, and therefore the term "treating" includes the step of sealing the metal surface, as needed. Additionally, "treating" can include process steps leading up to and including painting, as needed. For example, the treatment step can include applying a decorative coating, such as painting by electrocoating. After applying the pretreatment solution, the pretreatment solution can first be rinsed or dried in place, followed by painting. Each of these steps plays a role in the end product's ability to resist corrosion and minimize paint loss. As noted above, the treatment composition can be used as a chrome-free paint pretreatment solution.

[0017] As used herein, the term "metal," e.g., in the phrase "metal surface," includes aluminum, iron, zinc, and combinations thereof. Each listed metal includes both the elemental metal and its alloys; e.g., the term "aluminum" refers to aluminum and aluminum alloys. The term "alloy" refers to a metal in which the primary metal has the highest content of all other elements or a content equal to the highest content of all other elements (e.g., an aluminum alloy is a metal in which aluminum is present in an amount at least equal to the amount of every other element). Iron alloys include cold-rolled steel, electrogalvanized steel, and hot-dip galvanized steel. In some embodiments, the compositions of the present invention are used to treat types of metals including alloys of copper, brass, magnesium, aluminum, and iron.

[0018] As used herein, the term "compound of a Group IV-B element" refers to an acid and / or salt of a Group IV-B element, as described in U.S. Patent No. 5,859,106 to Jones et al., which is incorporated herein by reference. Such acids include fluorozirconic acid (HZrF), fluorotitanic acid (HTiF), and fluorohafnic acid (HHfF). An exemplary salt of a Group IV-B element is ammonium zirconium carbonate. Without being bound by any particular theory or explanation, it appears that a Group IV-B element, such as zirconium, increases the interaction between the composition and the metal surface, effectively helping to bond the composition to the metal surface.

[0019] The composition may further contain components that do not affect the basic and novel characteristics of the composition.For example, stabilizers may be added to improve the shelf life and stability of the composition.Stabilizers such as ammonium diborate may be particularly useful for this purpose.Without being held to theory, it is believed that stabilizers bind to free fluoride and buffer the solution, which prevents the free fluoride from reacting with other elements in the solution.For example, components such as stabilizers may be added to the composition without affecting the basic and novel characteristics.

[0020] The concentrations of the components of the composition, as well as the application temperature and residence time, can vary widely and can be modified in known ways depending on the desired coating weight. Furthermore, the desired coating weight is a function of, among other factors, the type of metal, the timing of processing after application of the pretreatment solution, the environmental conditions to which the treated metal will be exposed, and the type of decorative coating used. The coating process can be carried out by spraying, dipping, or flow coating techniques. The amount of coating should be sufficient to achieve the desired characteristics of the dried metal for its intended use. The desired coating amount is approximately 1.0 to 40.0 milligrams of dry coating per square foot of dry metal surface. Using a more concentrated solution allows for shorter processing times and / or lower temperatures to leave the desired amount of dry coating.

[0021] The component concentrations of the working baths of the metal pretreatment solutions of the present invention can vary over a wide range. The appropriate concentration ranges of the various components depend primarily on their solubility. Above the solubility limit, the solute may begin to precipitate out of solution. At concentrations that are too low, there are insufficient components to achieve the desired coating weight in a reasonable amount of time and to perform their function. Furthermore, these compositions can be provided as concentrates, but are generally utilized as dilutions with distilled water.

[0022] In an embodiment of the invention where the compound of Group IV-B elements is a combination of 45% fluorozirconate and 60% fluorotitanate, and the vanadate ion is ammonium vanadate, the following ranges have been used: about 0.01 to about 5.99 wt % fluorozirconate (as HZrF); about 0.01 to about 5.99 wt % fluorotitanate (as HTiF); and about 1.0×10 ammonium vanadate. -4 to approximately 5.0 × 10 -1In some embodiments, the ranges are 2.0 to 4.0 wt% fluorozirconate (as HZrF), 1.25 to 3.25 wt% fluorotitanate (as HTiF), and 1.0×10 ammonium vanadate. -1 to 4.0 x 10 -1 % by weight. The compositions set forth above are of concentrates. Of course, it may be desirable to ship the product in concentrate form. The working bath will be created by diluting the concentrate with a diluent (e.g., deionized water). The working bath concentration will be between about 1% and about 10% concentrate. In some embodiments, the working bath concentration will be between about 2% and about 3% concentrate. In some embodiments, the working bath concentration will be 2% concentrate.

[0023] The pH of the metal treatment solution of the present invention can vary over a wide range, as described above. The pH of the compositions of the present invention, such as those comprising water, a combination of fluorozirconate and fluorotitanate, and vanadium ions, is greater than or equal to 3. In particular, the pH of the composition may range from about 3 to about 6. In other embodiments, the pH may range from about 3 to about 5. In other embodiments, the pH may range from about 3 to about 4.5. In other embodiments, the pH may range from about 3.8 to about 4.2.

[0024] The metal treatment solutions of the present invention contain traces of molybdate ions, if any, that are undetectable. Conventional wisdom suggests that molybdate ions improve corrosion resistance, but as outlined below, this is not the case with respect to the neutral salt spray test outlined in MIL-DTL-81706B, Class 3. Such failure is believed to be the result of hydration of the molybdate ions within the oxide layer by sodium ions and water in the neutral salt spray. Under these conditions, the molybdate ions are removed from the oxide layer to form sodium molybdate. This formation creates gaps in the oxide layer. Corrosive agents can pass these gaps and potentially attack the metal underlying the oxide layer. As outlined below, molybdate-free solutions pass the neutral salt spray test outlined in MIL-DTL-81706B, Class 3. Solutions containing molybdate do not.

[0025] The metal treatment solution of the present invention is also inorganic. As a result, it does not contain aromatic carboxylic acids, particularly gallic acid. The reason for this elimination is that during post-treatment rinsing, the gallic acid is washed off and not present on the surface (i.e., discarded). Furthermore, when post-treatment rinsing is not used and a dry-in-place technique is utilized, the appearance of the coating is less uniform. Uneven coverage of the coating is undesirable because it results in uneven coverage of any paints subsequently applied.

[0026] Compositions according to the present invention may be made by mixing the components in any of several orders. The order of addition of the components is not critical. In one embodiment, vanadium ions are added to water, followed by the Group IV-B acid. In embodiments including a stabilizer, the stabilizer is added to the water first, then the vanadium ions are added to the solution, and finally the Group IV-B acid is added to the solution. This is typically all done as a concentrate, which is then diluted at the metal processing site before use.

[0027] Treatment of metal surfaces according to the present invention typically involves contacting the metal surface with an aqueous pretreatment composition consisting essentially of water, vanadium ions, a compound of a Group IV-B element, and optionally a stabilizer, the composition having a pH greater than or equal to 3. The method may further include cleaning and rinsing the metal surface with an aqueous cleaner prior to the rinsing step. The method may further include rinsing the metal surface with water after contacting the metal surface with the aqueous pretreatment composition, and then painting the metal surface. Alternatively, the pretreatment composition may be dried in place (i.e., without rinsing) and then painted.

[0028] Contacting the metal surface may be accomplished by any known coating technique, including, for example, spraying, dipping, roll coating, or flow coating. After contacting the optionally rinsed metal surface with the composition containing vanadium ions and a compound of a Group IV-B element, the metal surface is dried and then a decorative coating (e.g., paint) is applied, without rinsing between these steps. Thus, in this embodiment, the pretreatment is a "dry-in-place" pretreatment.

[0029] The cleaning step removes oil and other contaminants from the metal surface and is typically performed by immersing the metal surface in a bath of a silica-containing alkaline cleaning solution to form a cleaned metal surface. The silica-containing alkaline cleaning solution may be an aqueous solution of a silica-containing alkaline detergent. Such silica-containing alkaline cleaning solutions are sold under the trade name Bulk Kleen® by Bulk Chemicals Inc., Reading, Pennsylvania. Some exemplary silica-containing alkaline detergents that can be used according to the present invention include sodium carbonate, sodium hydroxide, and potassium hydroxide. In one embodiment, the detergent will be a silica-containing alkaline non-etching detergent. The detergent should not be an acidic detergent, as such detergents will etch the metal. The use of an acidic detergent will result in unsuccessful salt spray results. It is believed that such failure is caused by the acidic detergent exposing alloying elements or depositing material on the metal surface, increasing the potential for corrosion. In some cases, no cleaning may be necessary and this step may be omitted.

[0030] A metal surface that has been contacted with a silica-containing alkaline cleaning solution is referred to as a "cleaned metal surface." It is cleaned in the sense that it has been exposed to a silica-containing alkaline cleaning solution. However, it is not completely free of contaminants, as bath residues and other impurities may remain. Only after rinsing with water can it be considered completely clean and ready for contact with a pretreatment composition (i.e., substantially all of the impurities have been removed by that point). The rinse step is a conventional water rinse step, and in one embodiment, deionized water is used to remove any excess cleaning or detergent remaining on the metal surface from the cleaning step. The use of deionized water avoids the introduction of any harmful ions, such as chloride ions, into the system. After rinsing the metal surface, it is treated with an aqueous composition of the type previously described in accordance with the present invention.

[0031] One coating technique is reverse roll coating, in which a metal sheet is drawn between counter-rotating cylinders that rotate against the direction of travel of the unwound sheet. The solution flows down these cylinders until it contacts the metal. As the sheet metal passes between the cylinders in a direction against the direction of rotation of the cylinders, some wiping force is applied to the metal. Another conventional method is known as rapid dipping, in which the sheet metal is dipped into a batch containing the coating composition and then passed between two rolls to remove the excess. The concentration, temperature, and pH of the bath are interrelated. In one embodiment, the temperature of the bath during this contacting step is about 70°F to about 150°F, but the temperature can vary over a wide range depending on the concentration and pH. The pH of the bath depends on the specific pretreatment composition used.

[0032] After pre-treatment, the metal may then be dried (e.g., by blown air or by an oven). Temperatures for the drying operation may range from about 60°F to about 500°F. The length of the drying step will depend on the temperature utilized. Additionally, air may be blown onto the metal to enhance evaporation.

[0033] The desired performance characteristics of the present invention can be achieved by the processing steps described above to produce a pre-treated metal surface with good paint adhesion and corrosion resistance. These properties are obtained on the metal surface without a decorative coating. Thus, the treated metal surface can be used as an unpainted product and will exhibit corrosion resistance even if there is a delay between the treatment step and any subsequent painting.

[0034] Decorative paint coatings may be applied to dry metal surfaces. Typical, non-limiting examples of decorative coatings include paints and lacquers, including electrocoated paints. Suitable paints are available from several sources. A topcoat may be applied to the treated metal surface as a treated surface or as a treated and painted surface. For example, a suitable polyester triglycidyl isocyanurate (TGIC) powder coating topcoat is sold by DuPont, Wilmington, Delaware, under the trade name Alesta® AR. Typically, no rinsing is performed after contacting the rinsed metal surface with the treatment composition and applying the decorative coating. In this way, waste generation is minimized. The dry-in-place composition of the present invention serves to adhere the paint or lacquer to the metal and minimize corrosion.

[0035] The methods and compositions of the present invention can be applied in a wide variety of applications, including, by way of non-limiting example, extrusion applications and coil coating.

[0036] In short, the present invention provides an environmentally friendly composition and method for treating metals while still maintaining excellent paint adhesion and corrosion resistance. More specifically, the present invention avoids the use of chromium (both trivalent and hexavalent chromium) and its associated health hazards and waste disposal problems. Furthermore, as outlined below, contrary to industry belief, the addition of molybdate compounds does not appear to offer any benefits, and compounds containing molybdate consistently fail the neutral salt spray test under MIL-DTL-81706B, Class 3.

[0037] The compositions and methods of the present invention provide these benefits without the use of additional components that affect the basic and novel characteristics of the present invention. Other components, when added to the composition in sufficient amounts, may affect the novel characteristics. For example, certain components may destabilize the composition. Such components may cause the solution to polymerize, affecting the shelf life of the treatment solution. Other components may degrade the performance of the compositions and methods of the present invention. [Example]

[0038] The following examples are included to more clearly demonstrate the overall nature of the present invention. Examples 1-15 illustrate the improved results obtained by using the aqueous compositions of the present invention. These examples are intended to illustrate, but not limit, the present invention. [Table 1]

[0039] In all of the following examples, Composition 1, Composition 2, Composition 3, Composition 4, Composition 5, and Composition 6 refer to the solutions identified in Table 1 above.

[0040] Example 1 Composition 1

[0041] In Example 1, a 6061 alloy aluminum panel was treated by the following immersion process. First, the panel was cleaned for 3 minutes at 140°F in a 3% v / v treatment solution of Bulk Kleen® 842. Bulk Kleen® 842 is a lightly silica-containing alkaline cleaner that will etch aluminum. Second, the panel was rinsed for 30 seconds at ambient temperature. Third, the panel was rinsed for an additional 30 seconds at ambient temperature with deionized water. Fourth, the panel was immersed for 3 minutes at ambient temperature in a 3% v / v dilution of Composition 1, with the bath pH adjusted to 3.5 with Bulk Neutralizer® 10. Fifth, the panel was rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panel was dried for 5 to 10 minutes at a temperature ranging from 200 to 220°F. Seventh, all panels were exposed unpainted to neutral salt spray per ASTM B117 for 168 hours, and all panels failed to meet the requirements of MIL-DTL-81706B.

[0042] Example 2 Composition 1

[0043] In Example 2, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned for 2.5 minutes at 140°F with a 4.5% v / v treatment solution of Bulk Kleen® 686QC. Bulk Kleen® 686QC is an aggressive, acidic cleaner. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed for an additional 30 seconds with deionized water at ambient temperature. Fourth, separate panels were immersed for 3 minutes at ambient temperature in separate 3% v / v dilutions of Composition 1, with the pH of the individual baths adjusted to 3.0, 3.5, and 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds with deionized water at ambient temperature. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200 to 220°F. Seventh, all panels were exposed unpainted to neutral salt spray per ASTM B117 for 168 hours, and all panels failed to meet the requirements of MIL-DTL-81706B.

[0044] Example 3 Composition 1

[0045] In Example 3, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Bulk Kleen® 737G is a non-etching, silica-containing alkaline cleaner. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 3% v / v dilutions of Composition 1 for 3 minutes at ambient temperature, with the pH of the individual baths adjusted to 3.0 and 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at a temperature ranging from 200-220°F. Seventh, all panels were exposed unpainted to neutral salt spray per ASTM B117 for 168 hours, and all panels failed to meet the requirements of MIL-DTL-81706B.

[0046] Example 4 Composition 2

[0047] In Example 4, 6061 alloy aluminum panels were treated using the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 3% v / v dilutions of Composition 2 for 3 minutes at ambient temperature, with the pH of the individual baths adjusted to 3.0 and 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels failed to meet the requirements of MIL-DTL-81706B.

[0048] Example 5 Composition 3

[0049] In Example 5, 6061 alloy aluminum panels were treated using the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 3% v / v dilutions of Composition 3 for 3 minutes at ambient temperature, with the pH of the individual baths adjusted to 3.0 and 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels failed to meet the requirements of MIL-DTL-81706B.

[0050] Example 6 Composition 4

[0051] In Example 6, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 3% v / v dilutions of Composition 4 for 3 minutes at ambient temperature, with the pH of the individual baths adjusted to 3.0 and 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, without any paint, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed).

[0052] Example 7 Composition 4

[0053] In Example 7, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 2% v / v dilutions of Composition 4 for either 3 or 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0054] Example 8 Composition 5

[0055] In Example 8, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 2% v / v dilutions of Composition 5 for either 3 or 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0056] Example 9 Composition 4

[0057] In Example 9, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 3% v / v dilutions of Composition 4 for either 3 or 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0058] Example 10 Composition 5

[0059] In Example 10, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 3% v / v dilutions of Composition 5 for either 3 or 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 5 to 10 minutes at temperatures ranging from 200-220°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0060] Example 11 Composition 5

[0061] In Example 11, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 2% v / v dilutions of Composition 5 for either 1 minute, 2 minutes, 3 minutes, or 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed with deionized water for 10 seconds at ambient temperature. Sixth, one set of panels was dried at ambient temperature. The remaining panels were dried at 212°F for 6 minutes. Seventh, all panels were exposed unpainted to neutral salt spray per ASTM B117 for 168 hours, and all panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed).

[0062] Example 12 Composition 5

[0063] In Example 12, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in separate baths of 2% v / v dilutions of Composition 5 for 1, 2, 3, or 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 6 minutes at 212°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0064] Example 13 Composition 5

[0065] In Example 13, 6061 alloy aluminum panels were treated by the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in a 2% v / v dilution of Composition 5 for 5 minutes at ambient temperature, with the pH of each bath adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 6 minutes at 212°F. Seventh, all panels were exposed, unpainted, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). The panels also met the contact resistance requirements of MIL-DTL-81706B, Class 3 both before and after 168 hours of neutral salt spray exposure. Finally, all panels passed the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0066] Example 14 Composition 4

[0067] In Example 14, 6061 alloy aluminum panels were treated using the following immersion process. First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 135-140°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in a 3% v / v dilution of Composition 4 for 6 minutes at ambient temperature, with the bath pH adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 8 minutes at 125°F. Seventh, all panels were exposed, without any paint, to a neutral salt spray test per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed contact resistance testing before and after salt spray testing per MIL-DTL-81706B, Class 3.

[0068] Example 15 Composition 6

[0069] In Example 15, 6061 alloy aluminum panels were treated by the following immersion process: First, the panels were cleaned with a 15 g / L treatment solution of Bulk Kleen® 737G for 5 minutes at 130°F. Second, the panels were rinsed for 30 seconds at ambient temperature. Third, the panels were rinsed with deionized water for an additional 30 seconds at ambient temperature. Fourth, separate panels were immersed in a 2% v / v dilution of Composition 6 for 5 minutes at ambient temperature, with the bath pH adjusted to 4.0 with Bulk Neutralizer® 10. Fifth, the panels were rinsed for 10 seconds at ambient temperature with deionized water. Sixth, the panels were dried for 8 minutes at ambient temperature. Seventh, all panels, unpainted, were exposed to neutral salt spray per ASTM B117 for 168 hours. All panels met the requirements of MIL-DTL-81706B, Class 3 (i.e., no pitting was observed). Additionally, all panels passed the salt spray test and the contact resistance test before and after the wet tape adhesion test per MIL-DTL-81706B, Class 3.

[0070] All wet tape adhesion and contact resistance tests were performed by a third-party laboratory not affiliated with the applicant. Additionally, the neutral salt spray tests used in Examples 13, 14, and 15 were performed by a third-party laboratory not affiliated with the applicant.

[0071] While certain embodiments and examples have been illustrated and described above, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made to these details within the scope and kind of equivalents of the claims and without departing from the spirit of the present invention. For example, all ranges broadly set forth in this document are expressly intended to include within their scope all narrower ranges that are subsumed within the broader ranges. It is also expressly intended that the steps of the methods using the various compositions disclosed above are not limited to any particular order. According to a preferred embodiment of the present invention, for example, the following is provided: (Section 1) A chromium-free aqueous treatment solution for coating metal surfaces, which conforms to the neutral salt test outlined in MIL-DIL-81706B, comprising: Water and a compound of a Group IV-B element; Vanadium ions and and no molybdate ions. (Section 2) Item 1, wherein the compound of a Group IV-B element is selected from the group consisting of fluorozirconic acid, fluorotitanic acid, and fluorohafnic acid, or a mixture thereof. (Section 3) 3. The solution according to item 2, wherein the compound is fluorozirconate. (Section 4) Item 2. The solution according to item 1, wherein the vanadium ions are sodium vanadate, ammonium vanadate, or a mixture thereof. (Section 5) The vanadium ions are 1.0×10 -3 to 5.0 x 10 -1 Item 1. The solution according to item 1, wherein the compound is present in the solution at a concentration in the range of wt%. (Section 6) Item 1. The solution according to item 1, further comprising gallic acid. (Section 7) Item 1. The solution according to item 1, wherein the solution is inorganic. (Section 8) Item 1. The solution of item 1, wherein the solution has a pH greater than or equal to 3. (Section 9) 7. The solution according to claim 6, wherein the solution has a pH of 3.0 to about 5.0. (Section 10) Item 2. The solution according to item 1, wherein the compound is fluorozirconate and the vanadium ions are ammonium vanadate. (Section 11) A chromium-free aqueous treatment solution for coating metal surfaces, which conforms to the neutral salt test outlined in MIL-DIL-81706B, comprising: Water and a compound of a Group IV-B element; Vanadium ions and wherein said solution is inorganic and free of molybdate ions. (Section 12) Item 12. The solution according to item 11, wherein the compound of a Group IV-B element is selected from the group consisting of fluorozirconic acid, fluorotitanic acid, and fluorohafnic acid, or a mixture thereof. (Section 13) Item 12. The solution according to item 11, wherein the compound is fluorozirconate. (Section 14) Item 12. The solution according to item 11, wherein the vanadium ions are sodium vanadate, ammonium vanadate, or a mixture thereof. (Section 15) The compound is fluorozirconate, and the vanadium ions are ammonium vanadate. Item 12. The concentrate according to item 11, which is a concentrate. (Section 16) 12. The concentrate of claim 11, wherein the concentrate is diluted with water so that the concentrate is present in an amount between about 0.5% and 5% wt%. (Section 17) 1. A method for coating a metal surface, comprising immersing the metal surface in the solution of claim 1 for up to about 300 seconds, wherein the solution has a pH of between about 3.0 and about 4.0. (Section 18) 13. The method according to claim 12, wherein the metal surface is selected from the group consisting of zinc, zinc alloys, aluminum, aluminum alloys, galvanized steel, and alloys of zinc and aluminum. (Section 19) 1. A method for coating a metal surface, comprising spraying the metal surface with the solution of claim 1 for up to about 300 seconds, wherein the solution has a pH of between about 3.0 and about 4.0. (Section 20) 15. The method of claim 14, wherein the metal surface is selected from the group consisting of zinc, zinc alloys, aluminum, aluminum alloys, galvanized steel, and alloys of zinc and aluminum.

Claims

1. 1. A chromium-free aqueous treatment solution for coating metal surfaces, said solution comprising: Water and 1.35 wt% fluorozirconate (H ２ ZrF ６ as ) and 1.35 wt % fluorotitanic acid (H ２ TiF ６ and a mixture of 2.0×10 −1 wt % ammonium metavanadate A solution consisting of

2. The solution of claim 1 , wherein the solution is inorganic.

3. 10. The solution of claim 1, wherein the solution has a pH greater than or equal to 3.

4. 4. The solution of claim 3, wherein the solution has a pH of 3.0 to 5.0.

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