DE2819161A1 - AQUATIC ALKALINE ZINC BATH FOR ELECTRIC PLATING AND METHOD FOR DEPOSITING ZINC FROM THIS BATH - Google Patents

Description

The invention relates to electrochemical deposition of zinc. It is already an electrochemical deposition bath known from zinc with an alkaline electrolyte, which preferably contains alkali zincate, and a reaction product of a Polyalkyleneimine of molecular weight from 3OO to 1,000,000 and an organic quaternary ammonium halide which is halogen contains, the one nitrogen of the polyalkylenimine i.a a ratio can quaterndsieren from one mole of organic ammonium halide to two mole units of the polyalkyleneimine. Such Bath composition is described in commonly assigned US Pat. No. 3,853,718 Application disclosed.

This known bath but has not yet the desired high stability, and the coatings obtained with the bath with respect to ductility - not _t \ nd shine fully satisfactory. The invention is therefore based on the object of creating an alkaline zinc bath which has improved stability and the coatings produced therewith have higher gloss and ductility. The solution to the problem is given in the preceding claims.

It has surprisingly been found that much better results in terms of bath stability, gloss and ductility of the Zinc coatings are obtained when the bath is a short chain reaction product of a ^ polyalkyleneamine of one molecular weight in the range from 60 to 1000 and contains an organic ammonium compound, the concentration of the ammonium halide being affected, to quaternize or alkylate a nitrogen of the polyalkyleneamine, so that a plurality of quaternary nitrogen side

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chains arise.

The reaction goes as follows:

HN - fcH - CH - (CH ₀ ) - n3 - HI ■ U ^x 2 ', m ι Λ χι

R ₃ R ₃

in which: R is H, alkyl having 1 to 4 carbon atoms; R -OH, -H, -COOH, alkyl with 1 to 4 carbon atoms; R H, alkyl, hydroxyalkyl, Carboxyalkyl, alkoxy with 1 to 4 carbon atoms, · m 0 to 4; and n 1 to

■ 4- ·

XR- N ⁺ (R ^) ₃ II

X ~

in. X is halogen; R. H, alkyl having 1 to 4 carbon atoms; and R ^0H

CH ₂ -ClI- CH ₂

R - K ⁺ (R ₄ ).
I Χ "

• 2Γ

in which R, R, R. and X have the same meaning as indicated above. The resulting reaction product contains structural units as described above.

The invention is now based on a preferred embodiment. described.

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The invention relates to the electrochemical deposition of zinc using a bath which is a source of zinc ions, preferably in the form of metallic zinc in an amount of about 2 to 50 g / l, especially about 6 to 30 g / l, and a bath soluble multiple quaternary Compound contains; this compound is the reaction product of a polyalkyleneamine of molecular weight from about 60 to 1000 and an organic quaternary ammonium halide containing a halogen which can react with at least a quarter of the free amino groups of the polyalkyleneamine. According to the invention, the reaction product thus prepared in the bath in an amount of about 5 ^m S t "is 10 g / l, preferably 10 mg to 4 g / l.

The present invention is applicable to a wide range of zinc plating baths applicable, including those referred to as zinc acid baths or largely cyanide-free baths as well as those that are generally referred to as high to low cyanide-containing baths. In the zincate plating baths generally a mixture of zinc oxide and alkali is present. The amount of alkyl metal hydroxide can be about 50 to 200 g / l and the source of zinc ions is, as already mentioned, zinc metal,

The processing parameters are such that the bath can be operated at normal temperature and atmospheric pressure, though Temperatures of up to 55 ° C can be used. Temperatures in the range from about 15 to 45 ° C. are preferred. The cathode current density can be in the range of about 0.005 *> is 0.108 A / cm,

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the anode current di elite in the range of about 0.005 to 0.0 ^ 8 A / cm ² .

The zinc luster present in the bath of the present invention is one made from a polyalkyleneamine. The reaction product which is used as a zinc brightener in the bath according to the invention should be one which is soluble in the aqueous alkaline system. The polyalkylene amine, which is used as a reactant for the production of the brightener, is a polyethylene amine in which one or more hydrogen atoms can be substituted by a lower alkyl , that is an alkyl with 1 to 3 carbon atoms, such as methyl, ethyl, n Propyl and isopropyl, including the substitution derivatives in which one or more alkyl hydrogen atoms are replaced by a bath-compatible organic radical, such as carboxyl, esterified carboxyl, aldehyde, acetyl, ether-carbonyl, and other bath-compatible radicals, such as hydroxyl and amino. Particularly preferred is unsubstituted polyethylene amine, which is generally commercially available.

The polyethylene amine can be represented as a polymerization product of the formula I:

^R 1 ^R 2

HN -4CH - CK - (CH_) - ΝΪ- H ι L 2 'm ij η

in which: RH, alkyl with 1 to K carbon atoms} R “-OH ₁ -H, -CüOH, alkyl with 1 to h carbon atoms; R ₃ is H, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy having 1 to h carbon atoms; m 0 to 4 and η 1 to 24,

The Pol / alkylenaiain, preferably unsubstituted polyethylene amine,

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iiat has a molecular weight of about 00 to 1000 and is therein an essential difference to the brightener of the bath according to the already mentioned US Pat. No. 3,853,718. This difference leads to the surprising progress that stability of the bath as well as ductility and gloss of the zinc deposit with a short-chain Reaction product of a polyalkyleneamine of one molecular weight in the range of 60 to 1000 can be significantly improved.

The zinc brightener according to the invention preferably has several quaternary ammonium sites. One of the quaternaries is in the polyalkyleneamine repeating unit, while the side chain attached to the polyalkyleneamine quaternary would be the second place for a quaternary nitrogen. The multiple N-quaternary compound which can be used herein is obtained by reacting the compound of the formula II XRN ⁺ (R ₄ ) ₃

with the polyalkyleneamine described above, wherein in the

OTT
Formula means: R j

-CK ₂ - CH - CH, each of the% a group ax up to k carbon atoms and X a halogen,

As an example of such a connection, consider the connection below of formula III listed:

OH

Cl - CH ₂ - CH - CH ₂ - N ^{+ (CH} _{3) 3}

Cl "

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If one uses the nitrogen in the polymerization product of the formula I quaternized with the compound of formula II, wex-the products with Structural units of the formula IV below are obtained:

OH

g-CH- CH ₂ N ⁺ (CH)
Cl "

■ N

R,

Cl

Of course, other agents can also be present in the bath be to achieve other desired properties, such as Improving the scattering power of the bath in areas of low current density and improving the bath solubility of the components. Suitable The agents are anisaldehyde, glue, vinyl alcohol and the glycerol esters of polyvinyl alcohol, which have a molecular weight of> 000 to 20,000 to have. Other polymers that can be used are gelatin, Peptone and the like. In addition, chelating agents or Agents which complex with the zinc in the bath may be used, such as nitrilotriacetic acid and theirs various alkali metal salts, such as sodium salts, ethylenediaminetetraacetic acid and its water-soluble salts, like that Sodium salt and the like.

¥ ie stated above, the invention is based on cyanide-free Zi baths as well as zinc baths containing cyanide. In don the following Examples are the Tesfcergobiiisse with both bath types gebz'acht. Generally speaking, in the aqueous according to the invention alkaline bath for the electrochemical deposition of zinc

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INSPECTED

Source for Zinlcionen provided as well as an effective amount of a zinc brightener, namely a bath-soluble multiple quaternary compound, the reaction product of a polyalkyleneamine having a molecular weight of about 60 to 1000 and an organic quaternary ammonium halide containing a halogen which has at least a quarter of the free amino groups reacts in the polyalkyleneamine is. More specifically, the source of zinc ions is preferably zinc metal and is present in an amount of about 2 to 50 g / l, preferably 6-30 g / l; the “reaction product, which is defined in more detail above, is present in an amount of about 5 mg to 10 g / l, preferably 10 mg - h g / l. Example I (zincate bath) ι

A solution of 5 »7 mol of tetraethylene pentamine was 1 ^, 7 mol N- (3-chloro-2-hydroxypropyl) trimethylammonium chloride in the presence implemented by 3OO g of sodium hydroxide. The solution was refluxed for one hour. The product obtained was then in a Amount of 2 g / l mixed with 10 g / l zinc oxide and 100 g / l sodium hydroxide. With this bath solution were using a usual Hull-cell steel plates about 7 »62 χ 12.70cm in size plated at 21 ° C for about 10 minutes at 2A. The zinc coating obtained was uniform and semi-glossy.

Example II (zincate bath)

A solution of 1 mol of triethylenetetramine containing 25Ο g of sodium hydroxide was refluxed with 3 mol of N- (3 rom-2.-hydroxypropyl) trimethylammonium bromide for one hour. The product obtained was mixed in an amount of k g / l with 10.5 g / l zinc metal and 90 g / l sodium hydroxide. The electroplating was done in one

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Stirred the Hull line at about 27 C for about 10 minutes at one ampere. A smooth, semi-glossy zinc coating was obtained.

Example III

The product obtained from the two starting materials of Example I was mixed in an amount of 0.5 g / l with 7.5 g / l zinc metal, 120 g / l sodium hydroxide and 10 mg / l betaine of benzyl chloride and nicotinic acid. It was again electroplated in a Hull cell at about 3 ² C for about 10 minutes at 2 amperes. The zinc coating obtained was lustrous over a wide range of current densities.

Example IV

The product obtained from the two starting materials of Example II was mixed in an amount of 1 g / l with 6 g / l zinc metal, 80 ^ / l sodium hydroxide and 100 mg / l anisaldehyde bisulfite. In a Hull cell at about 2h ° C and with a plating time of about 10 minutes at 2Δ, the bath of this example resulted in a zinc coating that was shiny up to a current density of 0.054 A / cm and uniformly semi-shiny in the current density range above .

Example V

To a solution containing 5.7 moles of tetraethylene pentamine were added 1 * 1.7 moles of sodium hydroxide and 14.7 moles of N- (3-chloro ~ 2-hydroxypropyl) -trimethylammonium chloride given. The solution was heated to 90 ° for one hour and then allowed to cool overnight.

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The product resulting from Example V was vurde with a
Formulated source of zinc ions and cyanide. The results are given below.

Example VI

1.0 g / l of the compound of Example V were mixed with 34.0 g / l zinc metal, 75.0 g / l sodium hydroxide and 90.0 g / l sodium cyanide. With this solution, the test plates of the front
specified size in a Hull cell at room temperature and 2 A treated. The zinc plates obtained had a shiny appearance
Coating at a current density below 0.021 A / cm and a semi-glossy one at current densities above.

Example VII

In a further formulation, 0.5 g / l of the compound from Example V were mixed with 18.0 g / l of zinc metal, 75 g / l of sodium hydroxide and 4-5 g / l of sodium cyanide. At room temperature and 2 A, a tinplate was deposited on a cathode plate in a Hull cell
which was glossy and semi-glossy below 0.027 A / cm; end
at a current density above.

Example VIII ,

Another formulation was made from 50mg / l of a Realcüono product from a polyethyleneimine (MW 600, about 25 $ prim., 50 $ sec. and 25 $ tert. Amine) and N- (3-chloro-2-h3'droxipropyl) -trimetliylaramoniumclilD2id, 7i5gA zinlon metal, 67g / l sodium hydroxide "and 11.0g / l sodium cyanide. The electroplating was carried out on test plates of the

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given size in a Hull cell at room temperature with ZA on the cathode. The coating was glossy below about 0.019 A / cm and semi-glossy at current densities above.

Example IX

About 2.0 g / l of a reaction product from a polyethyleneimine

(MG 60p, about 25 $ prim., 50 $ sec . _{: and} 25 $ tertiary amine) and N- (i-ChIor-2- j

i hydroxipropyl) -trimethylammonium chloride were with 11.5g / l zinc metal, '

90.0g / l sodium hydroxide and 3 »75g / l sodium cyanide mixed.

2 '

Zinc coating produced on a Hull cell was shiny below 0.038 A / cm! and semi-glossy at current densities above. The coating var at room temperature and 2 A has been generated at the cathode.

As explained earlier, the invention is based in part on the discovery that by using a short-chain reaction product of a polyalkylenearain having a molecular weight in Range from 60 to 1000 with an organic ammonium halide containing a halogen which is used for quaternization or alkylation is capable of a nitrogen of the polyalkyleneamine, so that a plurality of quaternary nitrogens are generated gives much better results in terms of plating solution stability as well as the ductility and the gloss of the coatings obtained can be achieved. To take advantage of the present invention To make it even clearer compared to that from US Pat made cyanide-free zinc bath.

An alkaline zinc bath was prepared containing about 6.8 g / L zinc metal and about 80 g / L sodium hydroxide. This solution

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ORJGiNAL INSPECTED

was divided into roughly two equal portions. Part A 2 g / l of a multi-sticks were compounded from a polyalkyleneimine having a molecular weight of about 100,000 and N- (3-chloro-2-hydroxypropyl) trimethylammonium chloride admitted. For part B 2 g / l of a multi-nitrogen compound from a polyalkyleneamine, whose molecular weight was about 190.

In a Hull cell, which was operated at about 21 ^° C. and 2 A at the cathode, the following results were obtained after 30 minutes on commonly used steel plates: Both parts of the solution A and B led to shiny zinc coatings under the specified conditions, but solution led A to coatings that were less ductile than those obtained with solution B. On the other hand, after a prolonged plating time and the addition of known brighteners to the two solutions, solution A found a tendency to dull in areas of high current density, which is probably due to destruction by decomposition products. In areas of low current density, solution B was clearer and resulted in greater gloss than solution A.

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Claims (1)

28 593-21 DH.-ing. H. NEGENDANK -ίο «) · ΐ, ΐΡΐ ..- ΐ: α: .Η.HAÜCK · TJIPL.-PHYS. W ⁷ . SCHMITZ »IPL.-ING. E. GKAALFS divu-og. W, V ⁷ FiINSRr · dipl.-phys. W. CARSTENS HAMBUKG - MUNCiHEJf - Düsseldorf Dr.-Ing. W. Döring PATENTAxN WALTE · NEW AVALI. 41 2000 HAMBURG 30 2000 HAMBURG 38 NEW WALL 41 TELEPHONE (040) 36 74 29 X ^ ND 36 41 15, / Srj TELEX O 811 789 INPAT D _? Ö O / Oxy Metal Industries Corporation cablenegedapathnthambuhg P.O. BOX 20201 800OMUNCHENa-MOZARTSTNASSE 23 TELEPHONE (080) 0 38 0336 AND S3 24 80 Tvj. . _i_ · », ··. I r, ~ .r. ~ CABLE NEGED APATBNT MUNICH Detroit, me. 48220 4000 DÜSSELDORF 11 K.-WILH.-HING 41 USA TELEPHONE (0211) B7 OO 27'28 TBLEX 85 84 »SO DYNA D CABLE NEGEDAPATEXT DÜSSELDORF ADDRESS FOR SERVICE / PLEASE REPLYTO: HAMBURG, ^ 8. April 1978 Aqueous alkaline zinc bath for electroplating and process for the deposition of zinc from this bath ρ back: 1./Aqueous alkaline zinc bath for electroplating, marked features a source of zinc ions and an effective amount of a bath-soluble multi-quaternary atranonium compound as a zinc brightener, which is the reaction product of a polyalkyleneamine having a molecular weight of about 60 to 1000 and an organic quaternary ammonium halide, its
Halogen is able to react with at least a quarter of the free amino groups of the Polyalkylenainins ^. 2. Bath according to claim 1, characterized in that it is one of a polyalkylenearain of the formula I. 809846 / 07B0 R ₁ R ₉ , 1 j2 H - £ CH - CH - (CH ₂ ) - _m Nj ₁₁ H R ₃ R ₃ contains prepared quaternary ammonium compound, where in the formula: RH, alkyl with 1 to k carbon atoms; R ₂ -OH, H, -COOH, alkyl having 1 to 4 carbon atoms; RH, alkyl, hydroxyalkyl, carboxyalkyl, alkoxy with 1 to k carbon atoms; m 0 to k and η 1 to Zk, 3. Bath according to one of the preceding claims, characterized in that it consists of an organic quaternary ammonium halide of the formula II
XRN ⁺ (R ^) ₃
X " contains prepared quaternary ammonium compound, wherein OTT
R ι can be any of the R. radicals up to k carbon atoms -CH ₂ - CH - CH ⁴ and X is a halogen, H. Bath according to one of the preceding claims, characterized in that it contains a compound prepared from a polyalkyleneamine of the general formula I mentioned in claim 2 and a quaternary ammonium halide of the general formula II mentioned in claim 3 as a quaternary aramonium compound. 5. Bath according to one of the preceding claims, characterized 809846/0 750 draws that it is one of a polyalkyleneamine of the formula I. and a quaternary ammonium halide of formula III OH
Cl - CH - CH - CH ₂ - N ⁺ (CH) Cl " 3'3 contains produced quaternary ammonium compound. 6. Bath according to one of the preceding claims, characterized in that it contains a quaternary ammonium compound of the general formula IV
OH - CH - CH ₂ N
Cl " ι, οι ". in which R has the same meaning as in claim 2 general formula I. 7. Bath according to one of the preceding claims, characterized in that that there is zinc metal as a source of Zinlcionenquelle in an amount of about 2 to 50 g / l and the quaternary ammonium compound in contains an amount of about 5 mg to 10 g / l bath liquid. 8. Bath according to one of the preceding claims, characterized in that the zinc metal is present in an amount of about 6 to 30 g / l and the quaternary ammonium compound in an amount of about 10 mg to k g / l bath liquid. 809846/0750 9 «Process for separating zinc from a bath after a of claims 1 to 8, characterized in that an electrical Current from an anode through the bath to a cathodic workpiece in one for the deposition of a zinc coating sufficient time is passed through. 10 · The method according to claim ° », characterized in that the electrochemical deposition is carried out at a bath temperature of about 15 to about k $ C, a cathode current density of about 0.005 to 0.108 A / cm and an anode current density of about Makes 0.005 to 0.038 A / cm. 8098A6 / 07B0