MXPA05013979A - Aqueous acidic immersion plating solutions and methods for plating on aluminum and aluminum alloys - Google Patents

Abstract

The present invention provides a non-cyanide aqueous acidic immersion plating solution having a pH of from about 3.5 to about 6.5 and comprising zinc ions, nickel ions and/or cobalt iron ions, and fluoride ions. In one embodiment the immersion plating solutions of the invention also contain at least one inhibitor containing one or more nitrogen atoms, sulfur atoms, or both nitrogen and sulfur atoms. The present invention also relates to methods for depositing zinc alloy protective coatings on aluminum and aluminum alloy substrates comprising immersing the aluminum or aluminum alloy substrate in the non-cyanide acidic immersion plating solutions of the invention. Optionally, the zinc alloy coated aluminum or aluminum alloy substrate is plated using an electroless or electrolytic metal plating solution.

Description

METALIZED SOLUTIONS FOR IMMERSION IN AN AQUEOUS ACID AND METHODS TO METALIZE ON ALUMINUM AND ALLOYS OF ALUMINUM Field of the Invention This invention relates to solutions of metallization by immersion in aqueous acid and to a process for depositing a protective coating of zinc alloy on aluminum or aluminum alloy substrates. The invention also relates to metal substrates metallized with aluminum or aluminum alloy. BACKGROUND OF THE INVENTION One of the fastest growing markets in the world in the metal electrometalization / finishing industry is the processing and metallization of aluminum and its alloys. The unique physical and mechanical characteristics of aluminum make it particularly attractive to industries such as automotive, electronics, telecommunications and avionics, along with a large set of decorative applications. Among the most attractive properties of aluminum are its low overall density (2.7 g / cc), its high mechanical strength achieved by alloying it and treating it thermally and its relatively high resistance to corrosion. The additional properties of aluminum include a high thermal and electrical conductance, its magnetic neutrality, the high value of scrap and its amphoteric chemical nature. Aluminum articles for many applications are prepared from a variety of aluminum alloys including the alloying elements: silicon, magnesium, copper, etc. These alloy mixtures are formed to achieve enhanced properties such as high strength or ductility. The aluminum metallization and its alloys require specific surface preparations for a satisfactory electrolytic and non-electrolytic deposition. The most common practice used to achieve a satisfactory electrodeposition is to apply a zinc coating by immersion (better known as zinc plating) to the substrate just before plating. This process has long been considered the most economical and practical method of pretreating aluminum. The main benefits of applying a zinc plating plate for pretreatment are the relatively low cost of equipment and chemicals, wider operating windows for processing and ease of application of a controlled deposit. The presence of other metals in the zinc-coating solutions has an effect on the speed and efficiency on zinc deposition. Small amounts of alloying components (ie, Fe, Ni, Cu) not only improve the adhesion of the zinc deposit but also increase the instability of the zinc coating on a variety of aluminum alloys. For example, the addition of iron ions improves adhesion on alloys containing magnesium. The presence of nickel in the zinc plating improves the adhesion of metallized nickel directly on the zinc plating, and similar effects can be found with the addition of the copper in the zinc plating and the subsequent copper plating. In general, however, it has been demonstrated that the formation of zinc alloys provides finer and more compact deposits that efficiently translate into better adhesion of electrolytic / non-electrolytic plating downstream. On the other hand, the composition of an alloy zinc becomes more and more complicated with additional metal ions in the composition. It makes the selection of complexing agents more complicated and critical for the overall performance of the zinc. A zinc-iron-nickel composition is more sensitive than zinc-iron compositions for the selection of complexing agents and the proportion of metal ions in the composition. This becomes even more critical with the addition of copper ions in the alloy zinc. Due to its noble position in the galvanic series, the deposition rate of the copper in the zinc deposition by immersion is much higher than that of the other elements in the zinc plating. Thus, the control of copper deposition speed becomes important. It is possible to control the rate of copper deposition by selecting the agent or complexing agents suitable for copper ions and the appropriate proportion with the other metal ions. There are a few strong complexing agents for copper ions that offer good stability and performance of the alloy zinc, and cyanide seems to be the best candidate. Cyanide is a complex of choice for zinc-containing compositions containing copper and has been the industry standard for this application for many years. A negative aspect to using cyanide is the extremely toxic nature of cyanide and therefore, like other metallic finishing products, the search for a substitution for cyanide in the alloy zinc has been a topic of interest for many years. In recent years there have been some cyanide-free alloy zinc plating compositions that have been developed but these compositions still contain strong complexing agents such as EDTA, NTA, ethylenediamine, etc. to maintain the multiionic system in the stable form that makes the waste treatment of spent zinc-plating solutions as well as their 'rinses' more difficult. Zinc plating treatments are usually performed better also in multiple treatment mode. The pretreatment of the aluminum with a single dip in the zinc plating does not produce results as good as the process with double or triple dives in the zinc before the subsequent metallization stage. Such multiple zincing processes require more stages and processing time which means a more complicated and less productive and economical process. Therefore, like other metallic finishing products, the quest to replace conventional alkaline cyanide or cyanide-free alloy zinc for metal-on-aluminum has been a topic of interest in recent years. SUMMARY OF THE INVENTION The present invention provides a solution of dip coating of an aqueous acid without cyanide comprising zinc ions, nickel ions and / or cobalt ions, fluoride ions and optionally at least one inhibitor containing one or more nitrogen atoms, Sulfur atoms or both nitrogen and sulfur atoms. The present invention also relates to methods for depositing protective coatings of zinc alloy on aluminum and aluminum-based alloys which comprises immersing the aluminum or aluminum-based alloy in the acid-immersed plating solutions of the invention to deposit a coating Zinc alloy protector, optionally followed by metallizing the aluminum or aluminum alloy substrate coated with the zinc alloy using an electrolytic or non-electrolytic metallic metallized alloy. Detailed Description of the Invention The present invention, in one embodiment, refers to aqueous acid immersion plating solutions that do not have cyanide ions and more particularly to non-cyanide aqueous acid dip plating solutions that are useful for depositing a coating Protector of zinc alloy on aluminum and various substrates of aluminum-based alloy. Therefore, in one embodiment, the cyanide-free aqueous acid dip solutions of the invention have a pH of about 3.5 to about 6.5 and comprise zinc ions, nickel and / or cobalt ions and fluoride ions with the condition of the solution does not have cyanide ions. In another embodiment, the aqueous acid dip solution of the present invention may contain other metal ions such as copper ions, iron ions, manganese ions and zirconium ions and / or one or more metal complexing agents. In another embodiment, the solutions also contain an inhibitor that contains one or more nitrogen atoms, sulfur atoms or both nitrogen and sulfur atoms. The aqueous acid dip solutions of the present invention can be prepared by dissolving water soluble salts of the desired metals in water. Examples of the zinc ion source in immersion plating solutions include zinc fluoride, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, etc. Nickel ions can be introduced into the metallization solutions by acid immersion by dissolving nickel salts such as nickel acetate, nickel nitrate, nickel sulfate, etc. Cobalt ions can be introduced in the form of cobalt acetate, cobalt nitrate, cobalt sulfate, etc. The iron salts that are useful for introducing the optional iron ions include ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate, ferric nitrate, etc. Copper ions can be introduced by dissolving salts such as cuprous chloride, cuprous nitrate, cupric nitrate, cupric chloride, cuprous sulfate, cupric sulfate, etc. in water Other metal ions can be introduced by dissolving salts such as manganese (II) chloride, manganese (II) sulfate, zirconium chloride, magnesium chloride, magnesium sulfate, etc. In one embodiment, the dip metal solutions contain nickel ions but not cobalt ions. In another embodiment, the dip metal solutions contain nickel ions and cobalt ions. In yet another embodiment, the dip metal solutions contain cobalt ions but not nickel ions. Due to economic issues, the solutions contain nickel ions or a mixture of nickel with a small amount of cobalt. In one embodiment the concentration of the nickel ions or of the cobalt ions or of mixtures of cobalt ions and nickel ions is greater than the concentration of zinc ions. The dip-coating solutions of the present invention also contain fluoride ion. The fluoride ion source can be any soluble fluoride compound and so long as the ions introduced with the fluoride ion are not detrimental to the performance of the composition. Metal or ammonium fluorides can be used. Typical fluoride type materials include hydrofluoric acid, alkali metal or ammonium fluorides such as sodium fluoride, ammonium fluoride, etc. and alkali metal or ammonium hydrogen fluoride such as sodium hydrogen fluoride, ammonium hydrogen fluoride (ammonium bifluoride), etc. As a high solubility in water is desired where possible, highly soluble fluorides such as sodium bifluorides or ammonium are preferred. In one embodiment, the aqueous acid dip solution contains from about 0.005 to about 100 g / 1 of fluoride ions. The aqueous acid dip solutions of the present invention have a pH in the range of about 3.5 to about 6.5. In another embodiment, the pH of the solutions may vary from about 4.0 to about 6.0 and in yet another embodiment, the pH of the solutions is in the range of about 4.5 to about 5.5. In one embodiment, the aqueous acid dip solutions of the present invention will comprise from about 1 to about 150 g / 1 of zinc ions from about 5 to about 250 g / 1 of nickel and / or cobalt ions of about 0.005 to about 0.05 g / 1 of fluoride ion. In another embodiment, the aqueous acid plating solutions of the present invention may comprise from about 10 to about 30 g / 1 of zinc ions from about 20 to about 50 g / 1 of nickel and / or cobalt ions of about 0.5. to approximately 10 g / 1 of fluoride ion. In one embodiment, the concentration of zinc ions is lower than the concentration of nickel and / or cobalt ions. The aqueous acid dip solutions of the present invention may also contain at least one inhibitor containing one or more nitrogen atoms, one or more sulfur atoms or both nitrogen and sulfur atoms. In one embodiment, said nitrogen atoms are not present in an aliphatic amine or hydroxylamine. In another embodiment, the dip metal solutions of the invention also contain one or more metal complexing agents. Said solutions offer improved stability of the complete system and an acceptable performance in a variety of aluminum alloys and aluminum alloys. The dip-coating solutions of the present invention do not have cyanide ions said solutions offer the additional advantage of an environmentally-friendly application for the pre-treatment of various metal substrates such as aluminum and aluminum-based alloys. In another embodiment, the aqueous acid plating solutions of the invention do not have hard complexing agents including aliphatic amines such as EDTA, NTA, ethylenediamine, etc. Inhibitors useful in the dip-coating solutions of the present invention may be selected from a wide variety of compositions containing nitrogen and / or sulfur atoms. Therefore, in one embodiment, the inhibitor can be selected from one or more compounds characterized by the formula R2N-C (S) YI wherein each R is independently hydrogen or an alkyl, alkenyl or aryl group, and Y is XR1, NR2 or N (H) NR2, where X is O or S, and R1 is hydrogen or an alkali metal. Examples of such compounds include thioureas, thiocabamates and thiosemicarbazides. The thiourea compounds which can be used in the present invention can be characterized by the formula: [R2N] 2CS (II) wherein each R is independently hydrogen or an alkyl, cycloalkyl, alkenyl or aryl group. The alkyl, cycloalkyl, alkenyl and aryl groups may contain up to ten or more carbon atoms and substituents such as hydroxyamino and / or halogen groups. The alkyl and alkenyl groups may be straight or branched chain. The thioureas used in the present invention comprise thiourea or the various derivatives, homologs or analogs thereof recognized in the art. Examples of such thioureas include thiourea, 1,3-dimethyl-2-thiourea, 1,3-dibutyl-2-thiourea, 1,3-didecyl-2-thiourea, 1,3-diethyl-2-thiourea, 1, l-diethyl-2-thiourea, 1/3-diheptyl-2-thiourea, 1, l-diphenyl-2-thiourea, l-ethyl-l- (l-naphthyl) -2-thiourea, l-ethyl-l- phenyl-2-thiourea, l-ethyl-3-phenyl-2-thiourea, l-phenyl-2-thiourea, 1,3-diphenyl-2-thiourea, 1,1,3,3-tetramethyl-2-thiourea, l-allyl-2-thiourea, 3-allyl-l, l-diethyl-2-thiourea and l-methyl-3-hydroxyethyl-2-thiourea, 2,4-dithiobiuret, 2, 4,6-trithiobiuret, alkoxy ethers of isotiourea, etc. The thiocarbamates which can be used as inhibitors in the acid immersed plating solutions of the present invention include thiocarbamates represented by the formula R ^ CtSJ-XR1 III wherein each R is independently hydrogen or an alkyl, alkenyl or aryl group, X is O or S, and R1 is hydrogen or an alkali metal. The alkyl and alkenyl groups may contain from about 1 to about 5 carbon atoms. In another embodiment, the alkyl groups may each contain 1 or 2 carbon atoms. In still another embodiment, both R groups are alkyl groups containing 1 or 2 carbon atoms. Examples of said thiocarbamates include dimethylthiocarbamic acid, diethyldithiocarbamic acid, sodium dimethyldithiocarbamate hydrate, diethyldithiocarbamate sodium trihydrate, etc. The thiosemicarbazides which can be used as inhibitors in the acid immersed plating solutions of the present invention include thiosemicarbazides represented by the formula R2N ~ C (S) -N (J) NR2 IV wherein each R is independently hydrogen or a group alkyl, alkenyl or aryl. In one embodiment, the R groups are alkyl groups containing from 1 to 5 carbon atoms, and in another embodiment, the alkyl groups may each contain 1 or 2 carbon atoms. Examples of such thiosemicarbacias include 4,4-dimethyl-3-thiosemicarbazide and 4,4-diethyl-3-thiosemicarbazide. The aqueous acid dip solutions of the present invention may also contain as inhibitors one or more nitrogen-containing disulfides such as those represented by the formula [R2NCS2] 2 V in which each R is independently hydrogen or an alkyl group, alkenyl or aryl. The alkyl groups may contain from 1 to about 5 carbon atoms. In another embodiment, the alkyl groups may each contain 1 or 2 carbon atoms. In another embodiment both R groups are alkyl groups containing one or two carbon atoms. Examples of said organic disulfides include bis (di-ethylthiocarbamyl) disulfide (thiram) bis (diethylthiocarbamyl) disulfide, etc. Inhibitors which are useful in the present invention may also include nitrogen-containing heterocyclic compounds which may be substituted or unsubstituted. Examples of substituents include alkyl groups, aryl groups, nitro groups, mercapto groups, etc. The nitrogen-containing heterocyclic compounds may contain one or more nitrogen atoms and examples of such nitrogen-containing heterocyclic compounds include pyrroles, imidazoles, benzimidazoles, pyrazoles, pyridines, dipyridyls, piperazines, triazoles, benzotriazoles, tetrazoles, pyrimidines, etc. The nitrogen-containing heterocyclic compounds may also contain other atoms such as oxygen or sulfur. An example of a heterocyclic compound containing nitrogen and oxygen is morpholine and examples of nitrogen containing heterocyclic compounds containing nitrogen and sulfur include thiazoles, thiazolines and thiadiazolidines. In one embodiment, the inhibitor comprises one or more of the nitrogen-containing heterocyclic compounds described above that are substituted with a mercapto group. Specific examples containing nitrogen substituted with mercapto useful as inhibitors in the dip solutions of the present invention include: 2-mercapto-l-methyl imidazole; 2-mercaptobenzimidazole; 2-mercaptoimidazole; 2-mercapto-5-methyl benzimidazole; 2-mercaptopyridine; 4-mercaptopyridine; 2-mercaptopyrimidine (2-thiouracil); 2-mercapto-5-methyl-l, 4-thiadiazole; 3-mercapto-4-methyl-4H-l, 2,4-triazole; 2-mercaptothiazoline, 2-mercaptobenzothiazole, 4-hydroxy-2-mercaptopyrimidine; 2-mercaptobenzoxazole; 5-mercapto-l-methyltetrazole; and 2-mercapto-5-nitrobenzimidazole. Inhibitors which are useful in the dip metallization solutions of the present invention may also include alkali metal thiocyanates such as sodium thiocyanate and potassium thiocyanate. The thioalcohols and thioacids can also be included in the dip-coating solutions of the invention as inhibitors. Examples of these inhibitors include: 3-mercapto ethanol; 6 mercapto-1-hexanol; 3-mercapto-l, 2-propanediol; 1-mercapto-2-propanol; 3-mercapto-l-propanol; mercaptoacetic acid; 4-mercaptobenzoic acid; 2-mercaptopropionic acid; 3-mercaptopropionic acid. In one embodiment, the dip-coating solutions of the present invention may contain one or more of the inhibitors described above. In another embodiment, dip solutions contain two or more of the inhibitors described above. When included in the dip solutions, the amount of inhibitor can vary from about 0.0005 to about 5 g / 1 or more, and in another embodiment, the amount can vary from about 0.005 to about 0.05 g / 1. In one embodiment, the amount of inhibitor can vary from about 0.005 to about 100 g / 1. The dip-coating solutions of the present invention may also contain one or more complexing agents. The complexing agents are useful for solubilizing the metal ions in the plating solution. The amount of complexing agent included in the plating solutions of the invention may vary from about 5 to about 250 g / 1 or more. In one embodiment, the concentration of the complexing agent or agents is from about 20 to about 100 g / 1. Useful complexing agents may be selected from a wide variety of materials including those containing anions such as acetate, citrate, glycolate, lactate, maleate, pyrophosphate, tartrate, gluconate, glucoatetanoate, etc. Mixtures of two or more complexing agents can be used in the dip-coating solutions of the present invention. Specific examples of such complexing agents include sodium tartrate, sodium acetate, disodium tartrate, sodium gluconate, potassium gluconate, potassium acid tartrate, potassium sodium tartrate (Rochelle salt), etc.

The metal complexing agents which may be included in the dip-coating solutions of the present invention in some embodiments may also comprise aliphatic amines, aliphatic hydroxylamines or mixtures thereof. In another embodiment, the complexing agents above comprise a mixture of one or more aliphatic amine and / or aliphatic hydroxylamine and one or more of the other complex agents described above. The amount of amine included in the dip solutions of the present invention may vary from about 1 to about 50 g / 1. Examples of the amines that are useful include ethylenediamine, diaminopropane, diaminobutane, N, N, N, N-tetramethyldiaminomethane, diethylenetriamine, 3,3-aminobispropylamine, triethylenetetramine, onoethanolamine, diethanolamine, triethanolamine, N-methylhydroxylamine, 3-amino- 1-propanol, N-methyl ethanolamine, etc. In another embodiment, the dip-coating solutions of the invention do not have aliphatic amines and aliphatic hydroxylamine. The aqueous acid dip solutions of the present invention can be prepared by dissolving the various components mentioned above in water. The components can be mixed with water in any order. Organic acids such as acetic acid, lactic acid, etc. can be included in the metallizing solutions to adjust the pH of the solution. The following examples illustrate the aqueous acid dip solutions of the present invention. Unless otherwise indicated in the following examples or elsewhere in the description and / or claims, all parts and percentages are by weight, the temperatures are in degrees centigrade and the pressure is at or near atmospheric pressure.

Table I Examples A-H Table 2 Examples I-M * all parts are in g / 1, the rest is water. The cyanide-free acid immersion plating solutions of the present invention described above are useful for depositing zinc alloy protective coatings as pretreatment for aluminum and various aluminum alloys. In one embodiment, improved results are obtained when the plating solutions contain one or more of the inhibitors described above. The use of the inhibitors and the combination of the inhibitors and complexing agents described above in the investment metallization solutions is believed to be responsible, at least in part, for the improved performance of the dip metallization solutions of the present invention. The inhibitors affect the deposition rate of zinc alloys and provide a uniform fine coating on aluminum and aluminum alloys. Zinc alloy protective coatings weighing approximately 2-6 mg / ft2 can be obtained with the dip-coating solutions described herein. In addition to aluminum, the dip-coating solutions of the present invention are useful for depositing a protective coating of zinc alloy on various aluminum alloys including cast and forged alloys. Exemplary molded alloys include alloys 356, 380 and 383. Exemplary forged alloys include aluminum alloys of type 1100, 2024, 3003, 3105, 5052, 5056, 6061, 6063, and 7075. In one embodiment, the coating deposition zinc alloy shield utilizing acid immersed metallization solutions - of the present invention comprises pretreatment steps for an optional metallic plating of the aluminum or aluminum alloy substrates using an electrolytic or non-electrolytic metal plating solution. It should be understood that rinsings with water are generally used after each processing step. The first step in the optional pre-treatment process is to clean the aluminum surface of any grease, dirt or oil using for example suitable alkaline acid cleaners or solvents that are not aggressive. Suitable cleaners include lightly unsciled alkaline cleaners and lightly tilled alkaline cleaners, both being used in a temperature range of between about 49 to 66 ° C for about 1 to about 5 minutes. After cleaning, aluminum is usually rinsed in water. The attack of clean aluminum substrates is then carried out using conventional attackers that can be acidic or alkaline. Generally the acid attacker is used. In one embodiment, the attack solution may comprise 50% nitric acid. In the process used in the following examples, the attack solution used to remove excessive oxide from the aluminum surface is Alklean AC-2 (5% by volume) from Atotech USA, and this attack solution comprises phosphoric acid / sulfuric acid / fluoride. The aluminum or aluminum alloy is in contact with Alklean AC-2 for about one to two minutes at about 20-25 ° C. The attacked samples are then rinsed with water. The attacked aluminum surface is then degreased. Degreasing is a process in which excess dirt is removed from the aluminum surface. Degreasing can be done using a nitric acid solution (eg, a 50% by volume solution) or a mixture of nitric acid and sulfuric acid. In one embodiment, a typical degreasing solution for aluminum alloys may contain 25% by weight of sulfuric acid, 50% by weight of nitric acid, 25% by weight of ammonium fluoride. Degreasing can also be carried out with a mixture of nitric and sulfuric acids containing the product acid fluoride salt containing ammonium difluoride. In the examples that follow the aluminum alloys attacked are degreased using DeS utter NF (100 g / 1) from Atotech USA. at a temperature of about 20-25 ° C for about one minute and rinsed with water. DeSmutter NF comprises a mixture of acid salts and a persulfate-based oxidizing agent. A zinc alloy protective coating is applied to the etched aluminum substrate and degreased by immersing the aluminum substrate in a cyanide-free acid dip solution of the invention for a short period of time such as from about 100 to about 150 seconds to obtain a complete coating of the aluminum substrate. The temperature of the dip solution is generally maintained between about 20 ° C and 25 ° C. The excess metallization solution by immersion is removed from the surface of the aluminum substrate, generally by rinsing with water in deionized water. In the following Examples, the aluminum is immersed in the dip solution indicated at 20-25 ° C for about 120-150 seconds. After the acid immersion plating treatment described above, the aluminum substrates coated with the zinc alloy can be metallized with any suitable metal using electrolytic or non-electrolytic plating processes well known in the art. Suitable metals include nickel, copper, bronze, brass, silver, gold and platinum. In one embodiment, aluminum substrates coated with zinc alloy are metallized in non-electrolytic processes with nickel or electrolytic plating such as nickel sulfide or copper pyrophosphate etch solutions. The following examples 1-14 illustrate the deposition of a protective coating of zinc alloy according to the present invention on various aluminum alloys followed by metallic plating. For the plating tests, 1 inch by 4 inch (2.5 cm by 10 cm) aluminum alloy test plates with a thickness of 0.09-0.25 inch (0, 23-0.64 cm). All the test plates are cleaned, etched and degreased as described above before immersing them in metallized solutions by immersion in acid without cyanide of the invention. The metal layers are metallized at about 1 mil (25.4 μm) or a somewhat greater thickness before the adhesion test. In Examples 1-13, samples coated with zinc alloy are metallized with nickel using a Nichem-2500 electrolytic nickel bath (Atotech USA) for 90 minutes at about 95 ° C. In Example 14, the samples coated with zinc alloy are plated electrolytically in an electrometallized solution with copper pyrophosphate for 45 minutes at approximately 25 ASF of current density. The samples coated with zinc alloy of Example 15 are metallized in a nickel sulfamate electrolyte etch bath followed by electrometallization steps with bright acid copper, bright nickel and decorative chrome. The metallic metallized samples of Examples 1-15 are then rinsed with water, dried and tested for adhesion of nickel or other metallized metals to the aluminum substrate. The adhesion of the metallized metal is determined using one or more of the following tests. An adhesion test involves using a 90 ° torsion. In this test, after a 90 ° twist of the metallized sample, the inner and outer torsional surfaces of the twisted area are checked for peeling (descaling) of the metallized metal from the base aluminum substrate. The adhesion of the metallized metal is qualified as: good (0% detachment), normal (less than 10% detachment on either side of the twisted area) and bad (greater than 20% detachment). For molding alloys, the methods of "Reverse Saw", "Grinding" and "Cross Marking / Scratch" are used to check the adhesion of the metallized metal and the adhesion is qualified using the above criteria. Some metallized samples are also tested after hardening them at 150 ° C for two hours, cooling them in cold water (20 ° C), and the metallized surface is then analyzed for blisters using a "if it does not have blisters / raisins" criterion. and "if it has blisters / fails". Examples 1-10 The plating solutions of Examples AK and M are used to deposit a zinc alloy coating on forged aluminum alloys 2024 and 6061. Aluminum alloys coated with zinc alloy are then metallized in a nickel bath no electrolytic Nichem-2500 (Atotech USA) for 90 minutes at approximately 95 ° C. The metallized samples are rinsed with water, dried and tested for adhesion using the 90 ° torsion test described above. The results are summarized in the following Table III. Table III 90 ° Torsional Adhesion Test Results Example Alloy Solution Metallized Alloy by 2024 6061 Immersion of Example 1 A Good / Normal Normal 2 B Good Normal 3 C Good Good 4 D Good Normal 5 E Good Good 6 F Good Good 7 G Good Good 8 H Good Normal 9 I Good Normal J Good Good 11 K Good Good 12 M Good Good Example 13 Aluminum alloys including molding alloys 356 and 380, and forged alloys including 1100, 2024, 3003, 5052, 6061 and 7075 are coated with alloy zinc using the dip-coating solution of Example L followed by electroless nickel plating. The nickel-plated parts are tested for adhesion in the 90 ° torsion test and the cold water milling and quenching methods. All samples are classified as good. EXAMPLE 14 The aluminum alloys 2024 and 6061 are coated using the dip coating solution of Example L by the procedure described above. The samples coated with zinc alloy are then plated electrolytically in a copper pyrophosphate bath for 45 minutes at approximately a current density of 25 ASF. The copper-plated samples are tested for adhesion of the metallized copper to the aluminum alloy and adhesion failure is not observed in the 90 ° torsion test. EXAMPLE 15 The procedure of Example 14 is repeated except that the zinc alloy-coated parts are metallized in a nickel sulfamate electrolyte etch bath followed by electrometallization steps with bright acid copper, bright nickel and decorative chrome. These electrometallized samples are tested for adhesion using the 90 ° torsion test as well as the hardening test described above. No adhesion or blister losses are observed on the metallized surface of any of the metallized samples. Example 16 The procedure of Example 15 is repeated except that the dip solution from Example M is used to deposit the zinc alloy coating. No adhesion losses or blisters are observed on the metallized surface in any of the metallized samples. Although the invention has been explained in relation to its various embodiments, it should be understood that other modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention described herein is intended to cover such modifications that are within the scope of the appended claims.

Claims (45)

1. A solution of metalization by immersion in aqueous acid having a pH of about 3.5 to about 6.5 comprising zinc ions, nickel and / or cobalt ions and fluoride ions and at least one inhibitor containing one or more nitrogen atoms , one or more sulfur atoms or both nitrogen and sulfur atoms, with the proviso that the solution is free of cyanide ions and with the additional proviso that when the inhibitor contains one or more nitrogen atoms, said nitrogen atoms do not they are present in an aliphatic amine or hydroxylamine.

2. The dip-coating solution of claim 1 which also contains one or more complex, before-metal agents.

3. The dip-coating solution of claim 1 which also contains one or more additional metal ions selected from copper ions, iron ions, manganese ions, magnesium ions and zirconium ions.

4. The dip-coating solution of claim 1 wherein the inhibitor is selected from nitrogen-containing disulfides; alkali metal thiocyanates, thiocarbamates; heterocyclic nitrogen-containing compounds; nitrogen-containing heterocyclic compounds substituted with mercapto, thioacids, thioalcohols, compounds characterized by the formula R2N-C (S) YI wherein each R is independently hydrogen or an alkyl, alkenyl or aryl group, and Y is XR1, NR2 or N (H) NR2, where X is 0 or S, and R1 is hydrogen or an alkali metal and mixtures thereof.

5. The dip coating solution of claim 1 wherein the inhibitor is a thiourea compound represented by the formula: [R2N] 2CS II wherein each R independently hydrogen or an alkyl, alkenyl or aryl group.

6. The dip-coating solution of claim 1 wherein the inhibitor is at least one heterocyclic nitrogen-containing compound or heterocyclic compound containing mercapto-substituted nitrogen, or mixtures thereof.

7. The dip-coating solution of claim 6 wherein the heterocyclic compound is selected from pyrroles, imidazoles, benzimidazoles, pyrazoles, pyridines, piperazines, pyrazines, piperidines, pyrimidines, thiazoles, thiazolines, thiazolidines, rhodamines and morpholines.

8. The dip-coating solution of claim 1 wherein the inhibitor is a heterocyclic compound containing nitrogen substituted with mercapto.

The dip-coating solution of claim 1 containing: from about 1 to about 150 g / 1 of zinc ions from about 5 to about 250 g / 1 of nickel and / or cobalt ions

10. The dip-coating solution of claim 9 wherein the solution also contains from about 0.0005 to about 5 g / 1 of an inhibitor containing one or more nitrogen atoms, one or more sulfur atoms or both carbon atoms. Sulfur and nitrogen.

11. The dip coating solution of claim 1 which is free of aliphatic amines and aliphatic hydroxylamines.

12. A solution of dip-coating in aqueous acid having a pH of about 3.5 to about 6.5 and comprising: from about 1 to about 150 g / 1 of zinc ions, from about 5 to about 250 g / 1 of nickel and / or cobalt ions from about 0.005 to about 100 g / 1 of fluoride ion, and from about 0.005 to about 100 g / 1 of an inhibitor which contain one or more nitrogen atoms, one or more sulfur atoms or both atoms of sulfur and nitrogen. with the proviso that the solution does not have cyanide ions and with the additional proviso that when the inhibitor contains one or more nitrogen atoms, said nitrogen atoms are not present in an aliphatic amine or hydroxylamine.

13. The dip coating solution of claim 11 which also contains at least one metallic complexing agent.

14. The dip-coating solution of claim 13 wherein the metallic complexing agent is selected from an acetate, citrate, glycolate, lactate, maleate, pyrophosphate, tartrate, gluconate or glucoheptanoate and mixtures thereof.

15. The dip-coating solution of claim 12 wherein the inhibitor is selected from nitrogen-containing disulfides, alkali metal thiocyanates, alkali metal thiocarbamates, heterocyclic nitrogen-containing compounds, mercapto-substituted heterocyclic nitrogen-containing compounds, thioacids , thioalcohols, compounds characterized by the formula R2N-C (S) YI in which each R is independently hydrogen or an alkyl, alkenyl or aryl group, and Y is XR1, NR2 or N (H) NR2, where X is 0 or S, and R1 is hydrogen or an alkali metal and mixtures thereof.

16. The dip metalized solution of claim 12 wherein the inhibitor is a thiourea compound represented by the formula [R2N] 2CS II wherein each R is independently hydrogen or an alkyl, alkenyl or aryl group.

17. The dip-coating solution of claim 12 wherein the inhibitor is at least one heterocyclic nitrogen-containing compound or a heterocyclic compound containing mercapto-substituted nitrogen, or mixtures thereof.

18. The dip-coating solution of claim 17 wherein the heterocyclic compound is selected from pyrroles, imidazoles, pyrazoles, triazoles, tetrazoles, thiazoles, thiazolines, thiazolines, thiazolidines, pyridines, pyridines, piperazines, pyrazines, piperidines, pyrimidines and morpholines .

19. The dip-coating solution of claim 12 wherein the inhibitor is a heterocyclic compound containing nitrogen substituted with mercapto.

The immersion plating solution of claim 12 has a pH of about 4 to about 6.

The dip-coating solution of claim 12 which also contains one or more metal ions selected from copper ions, iron ions, manganese ions, magnesium ions and zirconium ions.

22. The dip-coating solution of claim 12 which is free of aliphatic amines and aliphatic hydroxylamines.

23. A non-cyanide aqueous acid immersion plating solution having a pH of about 4 to about 6 and comprising: from about 10 to about 30 g / 1 of zinc ions, from about 20 to about 50 g / 1 of nickel ions and / or cobalt, from about 0.5 to about 10 g / 1 of fluoride ion, and from about 0.005 to about 0.05 g / 1 of an inhibitor containing one or more nitrogen atoms, one or more sulfur atoms or both sulfur and nitrogen atoms with the proviso that when the inhibitor contains one or more nitrogen atoms, said nitrogen atoms are not present in an aliphatic amine or hydroxylamine.

24. The dip coating solution of claim 23 which also contains: from about 1 to about 250 g / 1 of at least one metallic complexing agent.

25. The dip-coating solution of claim 23 wherein the inhibitor is a heterocyclic compound containing nitrogen substituted with mercapto.

26. A process for depositing a protective coating of zinc alloy on aluminum or aluminum-based alloy substrates comprising (A) immersing an aluminum or aluminum-based alloy substrate in a solution of metallization by immersion in aqueous acid of the claim 1 for a period of time sufficient to deposit the desired coating and (B) remove the coated substrate from the plating solution by immersion.

27. The process of claim 26 wherein the aluminum or aluminum-based alloy surface is cleaned, etched and degreased prior to immersion in the dip solution.

28. The process of claim 27 wherein the cleaning is carried out with an alkaline cleaner, acid or solvent and the attack is carried out with an alkaline or acid attack solution.

29. The process of claim 27 wherein the aluminum or aluminum-based alloy is rinsed with water after each step of cleaning, etching, degreasing and metallizing by immersion.

30. A process for depositing a protective coating of zinc alloy onto an aluminum-based or aluminum-based alloy substrate comprising (A) submerging a substrate in a metallizing solution by immersion in aqueous acid of claim 12 for a period of time sufficient to deposit the desired coating and (B) remove the coated substrate from the plating solution by immersion.

31. The process of claim 30 wherein the substrate surface is cleaned, etched and degreased before immersing it in the dip solution.

32. The process of claim 31 wherein the cleaning is carried out with an alkaline cleaner, acid or solvent and the attack is carried out with an alkaline or acid attack solution.

33. The process of claim 32 wherein the substrate is rinsed with water after each step of cleaning, etching, degreasing and metallizing by immersion.

34. A process for depositing a protective coating of zinc alloy on an aluminum or aluminum-based alloy substrate comprising (A) immersing a substrate in a metallizing solution by immersion in aqueous acid of claim 23 for a period of time sufficient for deposit the desired coating and (B) remove the coated substrate from the metallized solution by immersion

35. The process of claim 34 wherein the substrate surface is cleaned, etched and degreased prior to immersion in the dip solution.

36. The process of claim 35 wherein the cleaning is carried out with an alkaline cleaner, acid or solvent and the attack is carried out with an alkaline or acid attack solution.

37. The process of claim 35 wherein the substrate is rinsed with water after each step of cleaning, etching, degreasing, metallizing by immersion.

38. A process for depositing a metal coating on an aluminum or aluminum-based alloy substrate comprising (A) applying a protective coating of zinc alloy by immersion on the substrate by immersing the substrate in a solution of metallization by immersion in aqueous acid of the claim 1 and (B) metallizing the substrate coated with zinc alloy using a plating solution with electrolytic or non-electrolytic metal.

39. The process of claim 38 wherein the substrate surface is cleaned, etched and degreased prior to immersion in the dip solution.

40. The process of claim 39 wherein the cleaning is carried out with an alkaline cleaner, acid or solvent and the attack is carried out with an alkaline or acid attack solution.

41. A process for depositing a metal coating on an aluminum or aluminum alloy substrate comprising: (A) applying a protective coating of zinc alloy by immersion on the substrate by immersing the substrate in a solution of metallization by immersion in aqueous acid of claim 12 and (B) metallizing the substrate coated with zinc alloy using a plating solution with electrolytic or non-electrolytic metal.

42. The process of claim 41 wherein the substrate surface is subjected to alkaline, acid or solvent cleaning, acid etching and degreasing prior to immersion in the dip solution.

43. The process of claim 42 wherein the cleaning is performed with an alkaline cleaner and the attack is carried out with an alkaline or acid attack solution. 44. An aluminum or aluminum-based alloy coated with metal obtained according to the process of claim 38. 45. An aluminum or aluminum based alloy coated with metal obtained according to the process of claim 39.

44. An aluminum or aluminum based alloy coated with metal obtained according to the process of claim 41.

45. An aluminum or aluminum-based alloy coated with metal obtained according to the process of claim 42.