Methods to maintain and / or improve adhesion after anodizing aluminum or titanium substrates bonded together with curable compositions

Abstract

Provided herein is a method of preparing a bonded anodized metal assembly, comprising the steps of: A. Providing a first metal substrate with a bonding surface and an opposite surface; B. Disposing onto at least a portion of the bonding surface of the first metal substrate a primer composition, said primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the Elements; C. Disposing a curable composition onto at least a portion of the primer-coated bonding surface of the first metal substrate, said curable composition comprising: An epoxy component and An anhydride component; D. Providing a second metal substrate with a bonding surface and an opposite surface; E. Optionally, providing and disposing onto at least a portion of the bonding surface of the second metal substrate the primer composition; F. Optionally, providing a curable composition onto at least a portion of the primer-coated bonding surface of the second metal substrate; G. Mating the curable composition-coated, primer-coated bonding surface of the first metal substrate and the second metal substrate, a bonding surface of which has optionally been primer coated and / or optionally curable composition coated, to form an assembly and exposing the assembly to conditions favorable and for a time sufficient to cure the curable composition to form a bonded metal assembly; H. Exposing the bonded metal assembly to anodizing conditions for a time sufficient to form a bonded anodized metal assembly.

Description

METHODS TO MAINTAIN AND / OR IMPROVE ADHESION AFTER ANODIZING ALUMINUM OR TITANIUM SUBSTRATES BONDED TOGETHER WITH CURABLE COMPOSITIONSBACKGROUNDField

[0001] Provided herein is a method of preparing a bonded anodized metal assembly, comprising the steps of:A. Providing a first metal substrate with a bonding surface and an opposite surface;B. Disposing onto at least a portion of the bonding surface of the first metal substrate a primer composition, said primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the Elements;C. Disposing a curable composition onto at least a portion of the primer- coated bonding surface of the first metal substrate, said curable composition comprising:An epoxy component andAn anhydride component;D. Providing a second metal substrate with a bonding surface and an opposite surface;E. Optionally, providing and disposing onto at least a portion of the bonding surface of the second metal substrate the primer composition;F. Optionally, providing a curable composition onto at least a portion of the primer-coated bonding surface of the second metal substrate;G. Mating the curable composition-coated, primer-coated bonding surface of the first metal substrate and the second metal substrate, a bonding surface of which has optionally been primer coated and / or optionally curable composition coated, to form an assembly and exposing the assembly to conditions favorable and for a time sufficient to cure the curable composition to form a bonded metal assembly;H. Exposing the bonded metal assembly to anodizing conditions for a time sufficient to form a bonded anodized metal assembly.Brief Description of Related Technology

[0002] Prior efforts at improving corrosion resistance of adhesively bonded aluminum substrates have involved either applying a conversion coating to the aluminum substrates prior to adhesively bonding them together (see e.g., FIG. 1A) or exposing the aluminum substrates to be bonded to anodizing conditions and then adhesively bonding the anodized aluminum substrates with an adhesive composition, such as an epoxy-based adhesive composition (see e.g., FIG. 1 B).

[0003] Indeed, in one prior process, US Patent Application Publication No. 2013 / 0270120 (Yao) describes a system and process for reducing cosmetic defects such as black lines, and otherwise reporting to improve the final cosmetic appearance of anodized parts. In relevant part, reference may be to FIGs. 2 and 3 thereof together with the accompanying description. There, in sum and substance, a series of steps is described including providing a metal part, such as aluminum, and degreasing at a pH of 8-9 at a temperature of 25°C for a period of time of 180 seconds; rinsing with water at the same temperature and time; activating with nitric acid at the same temperature for a period of time of 30 seconds; rinsing with water again; polishing with an 80:20 mixture of phosphoric acid and sulfuric acid at a temperature of 85°C for a period of time of 180 seconds; rinsing with water again; de-smutting with nitric acid at a temperature of 25°C for a period of time of 120 seconds; anodizing with sulfuric acid at a temperature of 35°C for a period of time of 23-26 minutes followed by exposure to 14.5 to 15.5 volts; rinsing with water again; sealing with an acetate solution at a temperature of 95°C for a period of time of 30 minutes; and baking at a temperature of 85°C for a period of time of 10 minutes. See also International Patent Publication No. WO 2022 / 053954 (Larson), page 10.

[0004] These prior efforts have often failed to maintain the level of adhesion on aluminum substrates that the adhesive composition would ordinarily demonstrate but for exposure to anodizing conditions. More specifically, if one were to expose an adhesively bonded aluminum assembly to anodizing conditions in an effort to improve the outer surface finish for cosmetic reasons, oxidation of the substrates beneath the adhesive bond line can occur. Such oxidation can lead to fewer points of adhesive contact, which reduces overall adhesion performance.

[0005] And many recognized test methods for performing anodization exist. See e.g., ASTM B380-79 (2009)(“Standard specification for anodic oxide coatings on aluminum”) and ASTM D3933-98 (2017)(“Standard guide for preparation of aluminum surfaces for structural adhesive bonding (phosphoric acid anodizing”); see also ASTM B580, Type B and MIL-A-8625 Type II.

[0006] Accordingly, it would be desirable to provide a method for at least maintaining the level of adhesion on aluminum substrates that are anodized, and it would be particularly desirable to improve the adhesion demonstrated after exposing an assembly constructed with aluminum substrates to anodizing conditions.SUMMARY

[0007] The present disclosure provides a solution to those desires.

[0008] Provided herein is a method of preparing a bonded anodized metal assembly, comprising the steps of:A. Providing a first metal substrate with a bonding surface and an opposite surface;B. Disposing onto at least a portion of the bonding surface of the first metal substrate a primer composition, said primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the Elements;C. Disposing a curable composition onto at least a portion of the primer- coated bonding surface of the first metal substrate, said curable composition comprising:An epoxy component andAn anhydride component;D. Providing a second metal substrate with a bonding surface and an opposite surface;E. Optionally, providing and disposing onto at least a portion of the bonding surface of the second metal substrate the primer composition;F. Optionally, providing a curable composition onto at least a portion of the primer-coated bonding surface of the second metal substrate;G. Mating the curable composition-coated, primer-coated bonding surface of the first metal substrate and the second metal substrate, a bonding surface of which has optionally been primer coated and / or optionally curable composition coated, to form an assembly and exposing the assembly to conditions favorable and for a time sufficient to cure the curable composition to form a bonded metal assembly;H. Exposing the bonded metal assembly to anodizing conditions for a time sufficient to form a bonded anodized metal assembly.BRIEF DESCRIPTION OF THE FIGURES

[0009] FIG. 1 A depicts a flow chart of an anodizing process followed by adhesive application.

[0010] FIG. 1 B depicts a flow chart of a conversion coating process followed by adhesive application.

[0011] FIG. 2 depicts a flow chart of the inventive method.

[0012] FIG. 3 depicts a bar chart of adhesive performance with and without the application of a primer composition (BONDERITE M NT-1455) prior to application of the adhesive composition, using (1) no anodizing conditions afterwards and two different anodizing conditions, (2) chemical anodizing conditions, and (3) electrical anodizing conditions.

[0013] FIG. 4 depicts a bar chart of adhesive performance before and after exposure to anodizing conditions, both with and without the application of a primer (BONDERITE M NT-1455) prior to application of the adhesive composition, with a variety of adhesive compositions on a certain aluminum substrate set.

[0014] FIG. 5 depicts a bar chart of adhesive performance before and after exposure to anodizing conditions, both with and without the application of a primer composition (BONDERITE M NT-1455) prior to application of the adhesive composition, on a variety of substrates.DETAILED DESCRIPTION

[0015] As noted above, provided herein is a method of preparing a bonded anodized metal assembly, comprising the steps of:A. Providing a first metal substrate with a bonding surface and an opposite surface;B. Disposing onto at least a portion of the bonding surface of the first metal substrate a primer composition, said primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the ElementsC. Disposing a curable composition onto at least a portion of the primer- coated bonding surface of the first metal substrate, said curable composition comprising:An epoxy component andAn anhydride component;D. Providing a second metal substrate with a bonding surface and an opposite surface;E. Optionally, p and disposing onto at least a portion of the bonding surface of the second metal substrate the primer composition;F. Optionally, providing a curable composition onto at least a portion of the primer-coated bonding surface of the second metal substrate;G. Mating the curable composition-coated, primer-coated bonding surface of the first metal substrate and the second metal substrate, a bonding surface of which has optionally been primer coated and / or optionally curable composition coated, to form an assembly and exposing the assembly to conditions favorable and for a time sufficient to cure the curable composition to form a bonded metal assembly;H. Exposing the bonded metal assembly to anodizing conditions for a time sufficient to form a bonded anodized metal assembly.

[0016] In the method, the first metal substrate in step A. is selected from zinc, iron, aluminum, titanium and cold-rolled, ground, pickled, and hot-rolled steel and galvanized steel, and alloys thereof. Similarly, the second metal substrate in step D. is selected from zinc, iron, aluminum, titanium and cold-rolled, ground, pickled, and hot- rolled steel and galvanized steel, and alloys thereof.

[0017] Desirably, the first metal substrate is selected from aluminum, titanium, or alloys thereof, such as bare aluminum, and the second metal substrate is selected from aluminum, titanium, or alloys thereof, such as bare aluminum.

[0018] The first metal substrate and the second metal substrate may be constructed from the same metal. Or the first metal substrate and the second metal substrate may be constructed from different metals.

[0019] The first metal substrate may be washed, degreased and deoxidized prior to disposing a primer composition on at least a portion of the bonding surface thereof.

[0020] The second metal substrate may be washed, degreased and deoxidized prior to disposing a primer composition on at least a portion of the bonding surface thereof.

[0021] The first metal substrate and / or the second metal substrate may be washed with water, distilled or deionized, or simply filtered tap water, prior to disposition of the primer composition.

[0022] The first metal substrate and / or the second metal substrate may be degreased with a neutral to low alkaline solution having a mild detergent, prior to disposition of the primer composition.

[0023] The first metal substrate and / or the second metal substrate may be deoxidized under either strongly acidic or strongly alkaline conditions, prior to disposition of the primer composition.

[0024] The primer composition to be disposed on at least one of the first metal substrate (in step B.) and / or the second metal substrate (optionally, but desirably, in step E.) comprises an ion selected from titanium, zirconium, hafnium and combinations thereof.

[0025] The primer composition may comprise an ion selected from titanium, zirconium, hafnium and combinations thereof in an amount of from about 0.001 percent by weight to about 3.0 percent by weight, based on the total weight of the primer composition.

[0026] For instance, the primer composition may comprise one or more of hexafluorotitanic acid, hexafluorozirconic acid, and hexafluorohafnic acid.

[0027] Commercially available examples of the primer composition include BONDERITE M-NT 1455 and BONDERITE M-NT 5700, each of which are aqueous solutions, suspensions or dispersions containing 95+ percent by volume water. The 1455 includes propoxy propanol, poly(hydroxystyrene), N-methyl glucamine, methanal,and hexafluorotitanic acid; the 5700 includes propoxy propanol, poly(hydroxystyrene), N-methyl glucamine, methanal, silica and hexafluorotitanic acid.

[0028] The primer composition may be applied to one, some or all of the surface(s) of the substrates by spray coating, roller coating, electrocoating or dipping. The temperature of the primer composition when applied can vary over a wide range, but ordinarily it is preferably from about 20°C to about 75°C. After application of the primer composition to the substrates, the substrate may optionally be rinsed.

[0029] Next, the primer composition-applied substrate should be dried. Drying can be carried out by, for example, circulating air or oven drying. While room temperature drying can be employed, it is preferable to use elevated temperatures to decrease the amount of drying time required.

[0030] Following application of the primer composition, a curable composition to act as an adhesive is disposed in step C. and optionally, but desirably, in step F. on at least a portion of the primer composition-applied substrate. The curable composition is curable by exposure to elevated temperature conditions, such as within the range of from 120°C to about 220°C, such as from about 130°C to about 150°C.

[0031] The curable composition comprises an epoxy component selected from aliphatic epoxies, cycloaliphatic epoxies, aromatic epoxies and hydrogenated aromatic epoxies.

[0032] For instance, the aliphatic epoxies may be selected from commercially available ones such as Epodil 741 , Epodil 746, Epodil 747, Epodil 748, Epodil 759, Epodil 761 , Epodil 781 , Epodil 749, Epodil 750, Epodil 757, Epodil 777, Epodil 794, Epodil 733, and Epodil 762, each from Evonik Corporation.

[0033] The cycloaliphatic epoxies may be selected from commercially available ones such as Epalloy 5000 and Epalloy 5200, each from Huntsman Corporation, Celloxide 2021 P and EHPE3150, each from Daicel Corporation, Sinepoxy CER-4299 from Sinocure chemical group, TTA182 from Jiangsu Tetra New Material Technology Co., Ltd., jER YED 216D from Mitsubishi Chemical, Japan, and Epiol LD 204 from Kukdo Finechem Co., Ltd.

[0034] The aromatic epoxies may be selected from bisphenol A, F or E epoxy resins, and biphenyl epoxy resins. Commercially available examples include jER YL980, YL 983U, jER1750, YL 7890, YX8800, and YX4000 series, each from Mitsubishi Chemical, Japan.

[0035] The (partially and fully) hydrogenated aromatic epoxies may be selected from hydrogenated bisphenol A, F or E epoxy resins, and hydrogenated biphenyl epoxy resins. Commercially available examples of the hydrogenated bisphenol A epoxy resin include jER YX 8000D, jER YX 8034, and jER YX 8040, each from Mitsubishi Chemical, Japan.

[0036] The epoxy component in the curable composition should be present in an amount of about 25 percent by weight to about 60 percent by weight, such as about 35 percent by weight to about 50 percent by weight, desirably about 45 percent by weight of the curable composition.

[0037] The anhydride component may be methylhexahydrophthalic anhydride, hexahydrophthalic anhydride or a blend thereof. These anhydrides are available commercially from Dixie Chemicals, for instance. Other anhydrides may also be used. Some of these anhydrides include tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, NADIC methyl anhydride, dodecenylsuccinic anhydride, octadecenylsuccinic anhydride, octenylsuccinic anhydride, hexadecenylsuccinic anhydride or a blend thereof, available commercially from Dixie Chemicals. Some other anhydrides include RIKACID MTA-15, RIKACID HNA-100, RIKACID SA, RIKACID TMEG-S, RIKACID TMEG-100, RIKACID TMEG-100, RIKACID TMEG-200, RIKACID TMEG-500, RIKACID TMEG-600, RIKACID TMTA-C, RIKACID BT-100, RIKACID TDA- 100 or a blend thereof, available commercially from New Japan Chemical Co., Ltd. Still some other anhydrides include polyazelaic polyanhydride, polysebacic polyanhydride, succinic anhydride, polyanhydrides (AC-39) and biobased polyanhydrides(AC-986 and AC-987) or a blend thereof, available commercially from Broadview Technologies Inc.

[0038] The anhydride component in the curable composition should be present in an amount of about 25 percent by weight to about 50 percent by weight, such as about 30 percent by weight to about 40 percent by weight, desirably about 35 percent by weight of the curable composition.

[0039] The stoichiometric ratio between the epoxy component to the anhydride component in the curable composition should be between 1 :100 to 100:1 , such as between 50:100 to 100:50, desirably between 100:60 to 100:100.

[0040] The substrates are then brought together and mated so that an adhesive bond forms between the mated substrates thereby forming a metal assembly.

[0041] As a result of application of the primer composition followed by the adhesive composition to one or more of the substrates to form an assembly following step G., the assembly may be exposed to anodizing conditions in step H. to improve the surface appearance with at least maintaining, and oftentimes improving, adhesion of the substrates adhesively bonded together.

[0042] The anodizing conditions may be selected from a variety of offerings, all of which useful herein are known to the public. For instance, and as noted above, anodizing conditions may be found in ASTM B380-79 (2009)("Standard specification for anodic oxide coatings on aluminum”) and ASTM D3933-98 (2017)(“Standard guide for preparation of aluminum surfaces for structural adhesive bonding (phosphoric acid anodizing”); see also ASTM B580, Type B and MIL-A-8625 Type II.

[0043] In addition, anodizing conditions such as are described in US Patent Application Publication No. 2013 / 0270120 (Yao) may be used in whole or in part. There, anodizing conditions are described to include providing a metal part, such as aluminum, and degreasing at a pH of 8-9 at a temperature of 25°C for a period of time of 180 seconds; rinsing with water at the same temperature and time; activating with nitric acid at the same temperature for a period of time of 30 seconds; rinsing with water again; polishing with an 80:20 mixture of phosphoric acid and sulfuric acid at a temperature of 85°C for a period of time of 180 seconds; rinsing with water again; desmutting with nitric acid at a temperature of 25°C for a period of time of 120 seconds; anodizing with sulfuric acid at a temperature of 35°C for a period of time of 23-26 minutes followed by exposure to 14.5 to 15.5 volts; rinsing with water again; sealing with an acetate solution at a temperature of 95°C for a period of time of 30 minutes; and baking at a temperature of 85°C for a period of time of 10 minutes.

[0044] As noted, the present invention confers many benefits and advantages included among them being provision of at least one, desirably at least two and preferably all three, of: improved initial adhesion; improved adhesion retention after exposure to anodization conditions; and improved post-anodization adhesion.

[0045] More specifically, through the practice of the inventive method one or more of an improvement of initial adhesion by 20.0-40.0% before exposure to anodizing conditions may be observed; an improvement of adhesion by 20.0-80.0% after exposure to anodizing conditions; and an improvement of adhesion retention of 80.0- 100.0% after exposure to anodizing conditions may be observed, particularly on aluminum substrates.

[0046] Also provided herein is:A bonded anodized metal assembly formed by the inventive method.A kit for (1) forming a bonded assembly comprising one or more substrates constructed from aluminum, titanium, or alloys thereof; (2) providing corrosion resistance to the bonded assembly after exposing the bonded assembly to anodizing conditions; (3) providing one or more of improved initial adhesion; improved adhesion retention after exposure to anodization conditions; and improved post-anodization adhesion; and (4) improved surface finish to the substrates, said kit comprising:A. A primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the Elements; andB. A curable composition comprising (i) one or more of an aliphatic epoxy, a cycloaliphatic epoxy, an aromatic epoxy or a hydrogenated aromatic epoxy and (ii) an anhydride.

[0047] The following examples are illustrative of the invention as described herein.EXAMPLES

[0048] In Table A below, examples (EX) and comparative examples (CE) are presented which have been made from the constituents listed above. Table A lists the curable compositions useful in the inventive method, noted as EX 1 , EX 2 and EX 3. Table A also lists the Part A composition of a two part curable composition used for comparative purposes referred to as CE 1 , CE 2, CE 3 and CE 4; Table B lists the Part B composition of CE 1 , CE 2, CE 3 and CE 4.Table ATable B

[0049] While CE 1 , CE 2, CE 3 and CE 4 are each formulated as two part curable compositions, when ready to use they function in the same manner as one part curable compositions. The main difference is shelf life preservation of two part curable composition, which ordinarily may be stored at room temperature.

[0050] The examples (EX 1 , EX 2, and EX 3) are cured at 150°C for a period of time of 1 hour. The comparative examples are cured differently. CE 1 , CE 2 and CE 3 may be cured at room temperature or under slightly elevated temperature conditions, such as 80°C or 120°C, for a period of time of 1 hour. CE 4 is cured at a temperature of 120°C for a period of time of 1 hour.

[0051] Tables 1-5 provide performance data captured using EX-1 as a curable composition and BONDERITE M-NT 1455 as a primer, where one is used. The substrates vary by table, as noted in the leftmost column of each table.

[0052] Where anodization is carried out, it is performed consistent with the relevant teaching of Yao.

[0053] Adhesion is measured by ASTM D-1002, Adhesive Lap Joint Shear Testing of Metals.Table 1Substrate Primer Anodization Adhesion Adhesion Adhesion[MPa] Improvement Retention[%] before [%] before and after and afterPrimer AnodizationAI6063 no No 23.72AI6063 Yes No 30.54 28.75AI6063 No Yes 21.12 89.04AI6063 yes Yes 30.14 42.7 98.69See also FIG. 5.Table 2Substrate Primer Anodization Adhesion Adhesion Adhesion[MPa] Improvement Retention[%] before [%] before and after and afterPrimer AnodizationAI7075 no No 29.28AI7075 Yes No 39.24 34.02AI7075 No yes 21.38 73.02AI7075 yes yes 36.94 72.78 94.14See also FIG. 5.Table 3Substrate Primer Anodization Adhesion Adhesion Adhesion[MPa] Improvement Retention[%] before [%] before and after and afterPrimer AnodizationTS-021 no No 25.3TS-021 Yes No 33.46 32.25TS-021 No yes 24.16 95.49TS-021 yes yes 30.16 24.83 90.13See also FIG. 5.Table 4Substrate Primer Anodization Adhesion Adhesion Adhesion[MPa] Improvement Retention[%] before [%] before and after and afterPrimer AnodizationTS-209 no No 24.06TS-209 Yes No 24.86 3.3TS-209 No yes 20.2 83.96TS-209 yes yes 24.52 21.39 98.63See also FIG. 5.Table 5Substrate Primer Anodization Adhesion Adhesion Adhesion[MPa] Improvement Retention[%] before [%] before and after and afterPrimer AnodizationTi no No 30.5Ti Yes No 39.36 29.05Ti No Yes 31.84 104.39Ti yes Yes 33.88 6.41 86.08See also FIG. 5.

[0054] The data captured in tabular form above and shown visually in FIG. 5 indicate an improvement through the use of the primer composition, before and after exposure to anodizing conditions. More specifically, the adhesion improves, the percent adhesion improves and the percent adhesion retention improves.

[0055] For instance, for the various aluminum substrates evaluated and data for which is captured in the tables above and depicted visually in FIG. 5:

[0056] In Table 1 , on AI6063 substrates, disposition of the primer composition ahead of the curable composition improved the initial adhesion by 28.75% (from 23.72MPa to 30.54MPa) before exposure to anodizing conditions; improved the adhesion by 42.7% (from 21.12MPa to 30.14MPa) after exposure to anodizing conditions; and improved adhesion retention after exposure to anodizing conditions - 98.69% compared to 89.04% without primer.

[0057] In Table 2, on AI7075 substrates, disposition of the primer composition ahead of the curable composition improved the initial adhesion by 34.02% (from 29.28MPa to 39.24MPa) before exposure to anodizing conditions; improved the adhesion by 72.78% (from 21 ,38MPa to 36.94MPa) after exposure to anodizingconditions; and improved adhesion retention after exposure to anodizing conditions -- 94.14% compared to 73.02% without primer.

[0058] In Table 3, on TS-021 substrates, disposition of the primer composition ahead of the curable composition improved the initial adhesion by 32.25% (from 25.3MPa to 33.46MPa) before exposure to anodizing conditions; improved the adhesion by 24.83% (from 24.16MPa to 30.16MPa) after exposure to anodizing conditions; and improved adhesion retention after exposure to anodizing conditions - 90.13% compared to 95.49% without primer.

[0059] In Table 4, on TS-209 substrates, disposition of the primer composition ahead of the curable composition improved the initial adhesion by 3.33% (from 24.06MPa to 24.86MPa) before exposure to anodizing conditions; improved the adhesion by 21 .39% (from 20.2MPa to 24.52MPa) after exposure to anodizing conditions; and improved adhesion retention after exposure to anodizing conditions - 98.63% compared to 83.96% without primer.

[0060] These improvements are significant and not expected individually, let alone collectively.

Claims

What is Claimed is:

1. A method of preparing a bonded anodized metal assembly, comprising the steps of:A. Providing a first metal substrate with a bonding surface and an opposite surface;B. Disposing onto at least a portion of the bonding surface of the first metal substrate a primer composition, said primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the Elements;C. Disposing a curable composition onto at least a portion of the primer- coated bonding surface of the first metal substrate, said curable composition comprising:An epoxy component andAn anhydride component;D. Providing a second metal substrate with a bonding surface and an opposite surface;E. Optionally, providing and disposing onto at least a portion of the bonding surface of the second metal substrate the primer composition;F. Optionally, providing a curable composition onto at least a portion of the primer-coated bonding surface of the second metal substrate;G. Mating the curable composition-coated, primer-coated bonding surface of the first metal substrate and the second metal substrate, a bonding surface of which has optionally been primer coated and / or optionally curable composition coated, to form an assembly and exposing the assembly to conditions favorable and for a time sufficient to cure the curable composition to form a bonded metal assembly;H. Exposing the bonded metal assembly to anodizing conditions for a time sufficient to form a bonded anodized metal assembly.

2. The method of Claim 1 , wherein the first metal substrate is selected from the group consisting of zinc, iron, aluminum, titanium, and cold-rolled, ground, pickled, and hot-rolled steel and galvanized steel, and alloys thereof.

3. The method of Claim 1, wherein the second metal substrate is selected from the group consisting of zinc, iron, aluminum, titanium and cold-rolled, ground, pickled, and hot-rolled steel and galvanized steel, and alloys thereof.

4. The method of Claim 1 , wherein the first metal substrate and the second metal substrate are constructed from the same metal.

5. The method of Claim 1, wherein the first metal substrate and the second metal substrate are constructed from different metals.

6. The method of Claim 1 , wherein the first metal substrate is selected from the group consisting of aluminum, titanium, and alloys thereof.

7. The method of Claim 1, wherein the second metal substrate is selected from the group consisting of aluminum, titanium, and alloys thereof.

8. The method of Claim 1 , wherein the first metal substrate is bare aluminum.

9. The method of Claim 1, wherein the second metal substrate is bare aluminum.

10. The method of Claim 1 , wherein the first metal substrate has been washed.11 . The method of Claim 1 , wherein the second metal substrate has been washed.

12. The method of Claim 1 , wherein primer composition comprises an ion selected from the group consisting of titanium, zirconium, hafnium and combinations thereof .

13. The method of Claim 1 , wherein the primer composition is made using one or more of hexafluorotitanic acid, hexafluorozirconic acid, and hexafluorohafnic acid.

14. The method of Claim 1 , wherein the primer composition comprises an ion selected from the group consisting of titanium, zirconium, hafnium and combinations thereof in an amount of from about 0.001 percent by weight to about 1 .0 percent by weight, based on the total weight of the primer composition.

15. The method of Claim 1 , wherein the curable composition is curable by exposure to elevated temperature conditions.

16. The method of Claim 1 , wherein the curable composition is curable by exposure to elevated temperature conditions within the range of about 120°C to about 220°C.

17. The method of Claim 1 , wherein the curable composition comprises an epoxy component selected from the group consisting of aliphatic epoxies, cycloaliphatic epoxies, aromatic epoxies and hydrogenated aromatic epoxies.

18. The method of Claim 1 , wherein the curable composition comprises an anhydride component selected from the group consisting of methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, NADIC methyl anhydride, dodecenylsuccinic anhydride, octadecenylsuccinic anhydride, octenylsuccinic anhydride, hexadecenylsuccinic anhydride, polyazelaic polyanhydride, polysebacic polyanhydride, succinic anhydride and combinations thereof.

19. The method of Claim 1 , wherein the curable composition comprises an epoxy component in an amount of from about 45 percent by weight and an anhydride component in an amount of from about 35 percent by weight, based on the total weight of the curable composition.

20. The method of Claim 1 , wherein the optional step E. of providing a primer composition onto at least a portion of the bonding surface of the second metal substrate is performed.21 . The method of Claim 1 , wherein the optional step F. of providing a curable composition onto at least a portion of the primer-coated bonding surface of the second metal substrate is performed.

22. The method of Claim 1 , wherein the bonded anodized metal assembly provides at least one of: improved initial adhesion; improved adhesion retention after exposure to anodization conditions; and improved post-anodization adhesion.

23. The method of Claim 1 , wherein the bonded anodized metal assembly provides at least two of: improved initial adhesion;improved adhesion retention after exposure to anodization conditions; and improved post-anodization adhesion.

24. The method of Claim 1, wherein the bonded anodized metal assembly provides each of: improved initial adhesion; improved adhesion retention after exposure to anodization conditions; and improved post-anodization adhesion.

25. A bonded anodized metal assembly formed by the method of Claim 1.

26. The bonded assembly of Claim 25, providing at least one of: improved initial adhesion; improved adhesion retention after exposure to anodization conditions; and improved post-anodization adhesion.

27. A kit for (1) forming a bonded assembly comprising one or more substrates constructed from aluminum, titanium, or alloys thereof; (2) providing corrosion resistance to the bonded assembly after exposing the bonded assembly to anodizing conditions; (3) providing one or more of improved initial adhesion; improved adhesion retention after exposure to anodization conditions; and improved postanodization adhesion; and (4) improved surface finish to the substrates, said kit comprising:A. A primer composition comprising a metal ion selected from Group IV B transition metals of the Periodic Table of the Elements; andB. A curable composition comprising (i) one or more of an aliphatic epoxy, a cycloaliphatic epoxy, an aromatic epoxy, or a hydrogenated aromatic epoxy and (ii) an anhydride.

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