GB1603446A

GB1603446A - Electrodeposition of zinc

Info

Publication number: GB1603446A
Application number: GB1699178A
Authority: GB
Original assignee: Oxy Metal Industries Corp
Current assignee: Oxy Metal Industries Corp
Priority date: 1977-05-04
Filing date: 1978-04-28
Publication date: 1981-11-25
Also published as: AU519624B2; DE2819161C2; NL185359B; FR2389688B1; CA1119997A; JPS53137833A; NL7804809A; AU3572678A; DE2819161A1; JPS5628997B2; FR2389688A1; NL185359C

Description

(54) ELECTRODEPOSITION OF ZINC (71) We, OXY METAL INDUSTRIES CORPORATION, a Corporation organised under the laws of the State of California, United States of America, of 21441 Hoover Road, Warren, Michigan 48089, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- The present invention relates to the electrodeposition of zinc.

Electroplating-baths useful for the electrodeposition of zinc are known which comprise an alkaline electrolyte preferably containing alkali metal zincate and also containing a reaction product of a polyalkylenimine having a molecular weight from about 250 to 1, 000,000 and an organic quaternary ammonium halide which contains a halogen which will quaternize a nitrogen of the polyalkylenimine in a ratio of one mole of organic ammonium halide to two mole-units of the polyalkylenimine. A composition of this character is specifically disclosed in U. S.

Patent No. 3,853,718 dated December 10, 1974, and which is assigned to the assignee of the instant application.

While the inventive concept described in the mentioned patent has fulfilled a need long existing in the art, the present applicants have discovered that substantially improved results by way of plating solution stability as well as ductility and brightness of the zinc deposits are achieved by uitilization in the bath of a small chain reaction product of an aliphatic polyalkylenamine having a molecular weight in the range of 60 to less than 250 especially 60 to 190, the terminal nitrogen atoms of which are primary or secondary, and an organic quaternary ammonium halide containing a halide capable of quaternizing or alkylating a nitrogen of the polyalkylenamine so as to produce a plurality of nitrogen quaternary sites.

In general, the reaction proceeds as follows :

wherein: R'is H, or an alkyl group of 1-4 carbon atoms; RI is-OH, H,-COOH, or an alkyl group of I-4 carbon ; RI is H, an alkyl, hydroxyalkyl, or carboxyalkyl group, or an alkoxy group of 1-4 carbon atoms; m is 1-4 and preferably nit-24

wherein: X is halogen ;

R4 is H, or an alkyl group of 1-4 carbon atoms, wherein:

R', R2, R3, R4, X and m are defined as above, and n is 1 to 24.

The resulting reaction product contains structural units as previously described.

The present invention is directed to the electrodeposition of zinc accomplished by utilization of an electroplating bath incorporating therein a source of zinc ions, preferably provided by zinc metal, in an amount of 2 to 50 grams per litre, and more specifically 6 to 30 grams per litre, and a bath soluble multiple quaternary compound which is the reaction product of an aliphatic polyalkylenamine having a molecular weight of from 60 to less than 250, the terminal nitrogen atoms of which are primary or secondary, and an organic quaternary ammonium halide which contains a halogen atom capable of reacting with at least one-fourth of the available amino groups in the polyalkylenamine. Preferably the reaction product as thus formed in the bath is present in an amount ranging from 5 milligrams to 10 grams per litre, and more specifically, 10 milligrams to 4 grams per litre.

The present invention can be used in a wide variety of zinc electroplating baths, including those which are termed in the art as zincate or essentially cyanidefree baths, or to those commonly referred to as high to low cyanide-containing baths. In zincate plating baths there is generally present an admixture of zinc oxide and caustic soda. The amount of alkali metal hydroxide may range from 50 to 200 grams per litre, and the source of zinc ions is as earlier indicated.

Atmospheric temperature and pressure are normally employed, although temperatures of up to 55 C may be used, and even more preferably 15 to 45 C.

The cathode current density may vary from 5 to 100 amps per sq. ft., while the anode current density may range from approximately 5 to 35 amps per sq. ft.

The zinc brightening agent that may be employed in the present invention is one that employs as a reactant polyalkylenamine. It is to be appreciated that the reaction product that is to be used as a zinc brightener in the present invention is one that should be soluble in the aqueous alkaline system. The polyalkylenamine that is utilized is preferably a lower alkyl substitute of polyethylenamine, that is a polyethylenamine in which one or more of the hydrogens is substituted by a lower alkyl, such as a one to three carbon alkyl radical, such as methyl, ethyl, n-propyl or isopropyl and including the substitution derivatives in which one or more alkyl hydrogen atoms are replace by a bath compatible organic radical, for example, carboxyl, esterified carboxyl, aldehyde, acetyl, ether carbonyl, and other bath compatible radicals, such as the hydroxy or amino radicals. It is particularly preferred that the polyalkylenamine be unsubstituted polyethylenamines which are generally available to the public.

Polyethylenamines can be expressed as the polymerization product of the compound of Formula I ;

R'is H, or an alkyl group of t-4 carbon atoms; R2is-OH, H,-COOH, or an alkyl group of I4 carbon atoms ; R3 is H or an alkyl, hydroxyalkyl, or carboxyalkyl group, or an alkoxy group of 1-4 carbon atoms; m is 0-4 ; and n is I-24.

The polyalkylenamine, preferably unsubstituted polyethylenamine, may range from about 60 to less than 250 in molecular weight, and herein lies an important patentable distinction over the disclosure in commonly assigned U. S. Patent No.

3,853, 718 to which reference was earlier made. As was mentioned previously, by proceeding in accordance with the instant invention, markedly improved results by way of plating solution stability, as well as ductility and brightness of the zinc deposits are achieved by utilization in the bath of a small chain reaction product of a polyalkylenamine having a molecular weight in the range of 60 to less than 250.

The zinc brightening agent that s to be employed in the present case preferably has a plurality of nitrogen quaternary ammonium sites. One of the quaternaries is in the repeating polyalkylenamine unit, while the side chain attached to the quaternary of the polyalkylenamine would be the second site for a quaternary nitrogen. The multiple nitrogen quaternary that may be employed herein is one that may be obtained by reacting the compound of Formula II; XRNs (R'), (II) Xo with the aforementioned polyalkylenamine, wherein:

R'has up to 4 carbon atoms per RI group ; and X is a halogen.

A more specific formula representative of Formula II defined immediately aboveis;

When one quaternizes the nitrogen of Formula I polymerization products with the compound of Formula II, there is obtained products having some structural units of Formula III ;

As can be appreciated, other agents may be present in the bath in order to impart other desirable characteristics such as improving the throwing power of the bath to low current density areas, and improving the bath solubility of the components. Suitable agents are anisaldehyde, glue, polyvinyl alcohol and the glycerol esters of polyvinyl alcools having a molecular weight of 5,000 to 20,000.

Other polymers that may be employed are gelatin, or peptone. In addition, chelating agents, or agents that can form a complex with the zinc in the bath may also be utilized, such as nitrilo triacetic acid and the various alkali metal salts, such as the sodium salt, ethylene diamine tetra acetic acid, and its water soluble salts, such as the sodium salts.

As has been indicated above, the novel concepts of this invention are applicable to cyanide-free or zincate baths as well as to cyanide-containing zinc baths, and in the examples now to follow there will be set forth test data on both types of baths. Generally stated, there is provided in an aqueous alkaline zinc electroplating bath, a source of zinc ions and an effective zinc brightening amount of a bath soluble multiple quaternary compound which is the reaction product of a polyalkylene amine having a molecular weight of from about 60 to less than 250, and an organic quaternary ammonium halide which contains a halogen which will react with at least one-fourth of the available amino groups in the polyalkylene amine. More specifically, the source of zinc ions is preferably provided by zinc metal in the amount of 2 to 50 grams per litre, and to be more precise, approx imately 6 to 30 grams per litre, and a reaction product as herein defined which is present in the bath in an amount ranging from 5 milligrams to 10 grams per litre, and more particularly, 10 milligrams to 4 grams per litre.

The invention will be more fully understood when reference is made to the following examples, the first two and the test data following therefrom being directed to a zincate or cyanide-free bath.

Example I.

A solution of 5.7 mole of tetraethylene pentamine (MW = l89) was reacted with 14. 7 mole N- (3-chloro-2-hydroxypropyl) trimethyl ammonium chloride in the presence of 300 grams of sodium hydroxide. The solution was refluxed for I hour.

2 gAi of the product obtained was then mixed with 10 g/l of zinc oxide and 100 g/l of sodium hydroxide. Using a conventional Hull cell with the above described plating solution maintained at a temperature of about 70 F, steel panels measuring approximately 3 by 5 inches were plated in the bath just described for about 10 minutes at 2 amperes. The zinc deposit obtained was uniform and semi-bright.

Example II.

A solution of I mole triethylene tetramine (MW = 146) containing 250 grams sodium hydroxide was reacted with 3 moles of N- (3-bromo-2 hydroxy propyl) trimethyl ammonium bromide by refluxing for one hour. 4 g/I ot the resultmg product was mixed with 10. 5 gil of zinc metal and 90 g/l of sodium hydroxide. Plating was accomplished in a Hull cell at about 80 F for approximately 10 minutes at one ampere. An even, semi-bright zinc deposit was obtained.

Example III.

0.5 g/l of the product obtained in Example I was mixed with 7.5 g/l of zinc metal, 120 g/l of sodium hydroxide and 10 ma of a betaine made from benzyl chloride and nicotinic acid. Steel panels were plated as in Example I in a Hull cell maintained at about 90 F with a plating time of approximately ten minutes at 2 amperes. The zinc deposit obtained was observed to be lustrous over a wide current density range.

Example IV.

1 g/l of the product obtained in Example II was mixed with 6 g/l of zinc metal, 80 g/l of sodium hydroxide and 100 ma of anisaldehyde bisulphite. Steel panels were plated as in Example I in a Hull cell at about 75 F with a plating time of approximately 10 minutes at 2 amperes. The bath of this example provided a zinc deposit lustrous up to 50 ASF and uniformly semi-bright above that range.

To illustrate the invention further, there will now be described work performed with a cyanide zinc bath embodying the novel concepts of this invention.

Example V.

Preparation of the reaction product.

To a solution containing 5.7 moles of tetraethylene pentamine there was added 14. 7 moles of sodium hydroxide and 14. 7 moles of N- (3-chloro-2-hydroxy propyl) trimethyl ammonium chloride. The solution was heated to 90 F for one hour and allowed to cool overnight.

The resultant product obtained by proceeding in the manner set forth in Example V was further formulated with a source of zinc ions and cyanide to form plating baths in accordance with the invention. Examples of such plating baths are given in Examples VI, VII, VIII and IX.

Example VI. i. O gA of the reaction product of Example V was mixed with 34.0 g/t of zinc metal, 75.0 FJI of sodium hydroxide, and 90.0 g/i of sodium cyanide. Steel panels were plated as in Example I in a Hull cell, at room temperature and at 2 amperes.

There was obtained obtained a zinc plate deposit which was bright below about 20 ASF and semi-bright above this value.

Example VII.

0.5 g/i of the reaction product of Example V was mixed with 18. 0 g/l of zinc metal, 75 g/l of sodium hydroxide and 45.0 gAi of sodium cyanide. Steel panels were plated as in Example I in a conventional Hull cell at room temperature and 2 amperes in the cathode panel. The zinc deposit obtained was bright below 25 ASF and semi-bright thereabove.

As was stated hereinabove, one of the inventive contributions made by the present applicants is the discovery that by utilizing a small chain reaction product of a polyalkylene amine having a molecular weight in the range of 60 to less than 250 with an organic ammonium halide containing a halide capable of quaternizing or alkylating a nitrogen of the polyalkylene amine so as to produce a plurality of nitrogen quaternary sites, there is achieved substantially improved results by way of plating solution stability as well as ductility and brightness of the zinc deposits. In order to more fully illustrate this advance over the inventive concept set forth in commonly assigned U. S. Patent No. 3,853, 718, the following comparative data was developed in an essentially cyanide-free zinc electroplating bath.

Examples VIII and IX.

An alkaline zinc electroplating solution was prepared containing zinc metal in the amount of about 6.8 g/l and approximately 80 g/l of sodium hydroxide. This solution was divided into two essentially equal portions and to Part (A) (Example VIII) there was added 2 g/l of a multi-nitrogen compound derived from a polyalkyleneimine having a molecular weight of about 100, 000, and N- (3-chloro-2- hydroxy propyl) trimethyl ammonium chloride. To Part (B) (Example IX) there was added 2 g/l of a multi-nitrogen compound derived from a polyalkylenamine whose molecular weight was about 190.

In a conventional Hull cell, operated at approximately 70 F, with 2 amperes on the cathode, the following results were obtained after 30 minutes on the normally used steel plates. Both Parts (A) and (B) under the conditions stated produced bright zinc deposits, however, the deposit of Part (A) was less ductile than that obtained from Part (B). On the other hand, after a lengthy period of plating and the addition of known brighteners to the solutions containing Parts (A) and (B), there was observed a tendency with solution (A) toward dullness in the high current density areas apparently due to interference of break-down products.

In low current density areas, the Part (B) solution was more clear and of greater brightness than that of solution (A).

Claims

WHAT WE CLAIM IS : 1. An aqueous alkaline zinc electroplating bath, comprising a source of zinc ions, and an effective zinc brightening amount of a bath soluble multiple quaternary compound which is the reaction product of an aliphatic polyalkylenamine having a molecular weight of from 60 to less than 250, the terminal nitrogen atoms of which are primary or secondary, and an organic quaternary ammonium halide which contains a halogen atom which will react with at least one-fourth of the available amino groups in the polyalkylenamine.
2. A zinc electroplating bath as claimed in Claim 1, in which the source of zinc ions is zinc metal present in an amount of 2 to 50 grams per litre, and in which the said multiple quaternary compound is present in the bath in an amount ranging from 5 milligrams to 10 grams per litre.
3. A zinc electroplating bath as claimed in Claim 2 in which the source of zinc ions is zinc metal present in an amount of 6 to 30 grams per litre, and in which the multiple quaternary compound is present in the bath in an amount of from 10 milligrams to 4 grams per litre.
4. A zinc electroplating bath as claimed in Claim 1, 2 or 3 in which the poly alkylenamine has the formula :

wherein: R'is H, or an alkyl group of 1-4 carbon atoms; R'is-OH, H,-COOH, or an alkyl group of 1-4 carbon atoms; R 3is H, an alkyl, hydroxyalkyl, or carboxyalkyl group, or an alkoxy group of I-4 carbon atoms; m is I4 and n is I-24.
5. A zinc electroplating bath as claimed in any one of Claims I to 4 in which the organic quaternary ammonium halide has the formula : XRN@ (R4) 3 Xo wherein:

R'is H, or an alkyl group of I4 carbon atoms; and X is a halogen.
6. A zinc electroplating bath as claimed in Claim 5, in which the organic quaternary ammonium halide has the formula :

Cl
7. A zinc electroplating bath as claimed in any one of Claims I to 6 in which the reaction product has the formula:

wherein : R'is H, or an alkyl group of 1-4 carbon atoms; RI is-OH, H,-COOH, or an alkyl group of l-4 carbon atoms; RI is H, or an alkyl, hydroxylalkyl, or carboxyalkyl group, or an alkoxy group of 1-4 carbon atoms; mis I to4and n is I to 24.
8. A zinc electroplating bath as claimed in Claim I substantially as specifically described herein with reference to Examples I, II, III, IV, VI, VII and IX.
9. A method of depositing zinc from an aqueous alkaline zinc electroplating bath, which comprises passing an electric current from an anode through a bath as claimed in any one of Claims 1 to 8 to a cathodic workpiece for a period of time sufficient to form a zinc deposit.
10. A method of depositing zinc from an aqueous alkaline zinc electroplating bath, which comprises passing an electric current from an anode through a bath as claimed in any one of Claims 1 to 8 to a cathodic workpiece for a period of time sufficient to form a zinc deposit, the temperature of said bath being 15 C to 45 C., the cathode current density varying from 5 to 100 amps. per sq. ft., and the anode current density being from 5 to 35 amps. per sq. ft.
II. A method of depositing zinc as claimed in Claim 9 substantially as specifically described herein with reference to Examples I, II, III, IV, VI, VII and IX.
12. An article bearing an electrodeposit of zinc whenever made by a method as claimed in any one of Claims 9 to 11.