DE2005795A1 - Improvements to the electrodeposition of nickel - Google Patents

Description

DR. R. POSCHBNRIEDER

DR. E. "■ · TIMER

,, - :; ^ÜLLER ^ j ₁₁ 2005795

Ludle-Grahn-ütraS 38 XT.

T * l "toa 4437"

Albright A Wilson Ltd., Qldbur.y near Birmingham, Warwickshire (Great Britain)

Improvements to the electrodeposition of nickel

The invention relates to improvements in the electrodeposition of nickel, particularly for Production of bare galvanic coatings.

It has long been known to use a wide variety of acetylene compounds as "organic brighteners" in nickel plating solutions. It was claimed that the simultaneous presence of an organic Schwefe - / oxygen compound, a bare galvanic Nickeliiberzug from the solution etc.

can get. For example, U.K. patent 747 908 uses certain Acetylenic alcohols, especially 2-butyn-1,4-diol, in combination with an organic sulfur / oxygen off compound as a brightener in nickel galvanizing solutions for the production of bare galvanic parts. It is also from the British Patent 864 287 the use of AlIr,. ο 1-epoxy adducts in connection there is an organ; above Sulfur / Saaeratoff-V9rbindung in nickel electroplating solutions for the formation of very bright nickel blemishes

known * In the two literature references are the most different! organic sulfur / oxygen compounds named as suitable for combined use with the acetylene compounds listed in each case. The use of naphthalene-1,3,6-trlsulfonic acid is particularly recommended.

The "recipes" listed in the cited references relate in particular to the "Watt bath", d. H. on an electrolyte with dissolved nickel (II) sulfate (225 - 350 g / l), nickel (II) chloride (30 - 50 g / l) and boric acid (20 - 45 g / l). The use of naphthalene trisulfonic acid (sodium salt) with 2-butyn-1 / J · - dlol or with the adduct of 2-butyn-1,4-diol alt 2 Moles of ethylene oxide (often referred to as 1,4-di- (6-hydroxyethoxy) -2-butyne) in such baths or solutions too bare, galvanic nickel coatings. Will However, such brighteners in nickel electroplating * »g # quarrel with "high chloride"; d. H. If used in baths with 150-350 g nickel (II) chloride per liter, they are Electroplated coatings produced with them are unsatisfactory because they are brittle and susceptible to spontaneous crack formation are. These disadvantages cannot be remedied by adjusting the concentrations of the brighteners.

It has now been found that a nickel plating bath with a "high chloride content" (also) produces a particularly bright appearance and have flat galvanic nickel coatings produced, when a very specific combination of acetylene brighteners with a very small amount of a specific type of sulfur / oxygen compounds is used. In addition, such a combination of additives also possesses when used in other nickel electrolytes an improved smoothing effect compared to the additives known from the literature references mentioned. at These special acetylene additives are wrapped around

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a mixture of certain proportions of an oC-hydroxyacetylene compound and an alkylene oxide condensation product of such a compound * The invention also relates to Use of such a mixture in connection with saccharin or substituted saccharin in one concentration of at least 1 g / l. The use of saccharin leads to galvanic coatings of good flexibility, the show practically no tendency to spontaneous cracking.

The invention thus provides an aqueous electrolyte for nickel-plating which (a) at least 30 g / l of a nickel (II) salt, (b) 0.1-1.0 g / l of a mixture of acetylene compounds, including both an OC - Hydroxyacetylene compound as well as an alkylene oxide condensation product of an oC-hydroxyacetylene compound in a weight ratio of these condensation products to the OC -hydroxyacetylene compounds of 1.5: 1 to 7: 1 and (c) of 1.0 to 5.0 g / l of saccharin or a substituted one Contains saccharin.

The concept of the invention can be implemented with nickel electroplating electrolytes which contain at least 30 g / l of a nickel (II) salt. Such an electrolyte can be an electrolyte of the "Watt" type, which contains 225-350 g nickel (II) sulfate, 30-5Og nickel (II) chloride and 20-25 g boric acid per liter. In particular, however, the idea of the invention can be implemented with nickel electrolytes with a "high chloride content ¹¹ , ie with nickel electrolytes with 150-350 g / l nickel (II) chloride. Such electrolytes preferably contain 50-225 g nickel (II) sulfate per liter, 150 - 250 g Nicke1 (11) chloride and 30-5Og boric acid. However, electrolytes containing nickel (II) chloride in an amount of 150-350 g / l can also be used

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contain the only nickel salt, and electrolytes with other nickel salts, e.g. nickel (II) sulfamate, can be used.

The N-hydroxyacetylene compounds used have a Hydroxy group in «6-position to an acetylene compound on. Such compounds are preferably 6-alkynols the general formula:

R ₁ -CHOH-CSCR ₂

wherein R ₁ and Rg each denote a hydrogen atom or an alkyl, alkenyl or alkynol radical having 1-4 carbon atoms which may contain an amino or hydroxyl substituent.

Examples of such ⁰ ^ -alkynols are:

2-butyn-1,4-diol;

1-butyn-3-ol;

Propargyl alcohol (2-propyn-1-oil);

1-pentyn-3-ol;

4-methoxy-2-butyn-1-oil;

3-hexyn-2,5-diol;

4-diethylamino-2-butyne-1 oil; and

2,4-hexadiyne-1,6-diol.

The first three of the compounds mentioned are particularly suitable.

The alkylene oxide condensation products of ^ -hydroxyacetylene compounds which can be used according to the invention are formed by reacting a ^ .- alkynol with 1-20 moles, preferably 1-4 moles, of an alkylene oxide. The preferred alkylene oxide is ethylene oxide, although propylene oxide, epichlorohydrin, or epibromohydrin can also be used. Mixtures of eoloher alkylene oxides can also be condensed with the - ^ - alkynol, either simultaneously or in succession. The «* .- alkynol can be a compound of the formula R ₁ -CHOH-OSDR ₂ and in particular

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be a compound from the group mentioned. The condensate ion product can be according to any of the usual applied to the production of polyoxyalkylene ethers by condensation of an alcohol with an alkylene oxide Win procedure. The preferred condensation products are made from 2-butyn-1,4-diol, 1-butyn-3-ol or Propargyl alcohol made with about 2 moles of ethylene oxide.

The acetylene compounds mentioned are in electrolytes according to the invention in a total concentration of 0.1 - 1.0 g / l used. Here a larger ^

Amount (by weight) of oC alkynol / alkylene oxide condensation product used as amount (by weight) of the simple oC alkynol. The weight ratio of condensate to oG-Alkynol is 1.5: 1 to 7: 1. This ratio is preferably 2: 1 to 5.5: 1, since with a higher ratio there is a tendency for the formation of holey coatings, while with a ratio below 2.0: 1 the smoothing effect of the additive can be impaired.

The electrolytes according to the invention contain 1.0 to 5.0 g of saccharin or a substituted saccharin. By "substituted saccharin" is to be understood an o-carboxybenzsulfimide which contains a core substituent, "for example an alkyl, halogen or sulfo substituent. Nevertheless, saccharin is preferably used as such. It has been found that the use of a saccharin compound is of essential importance in order to obtain galvanic coatings improved with nickel electrolytes with "high chloride content", in particular smooth, even and pliable coatings. In nickel electrolytes according to the invention, a Sac: -bai: in concentration of 1.5 to 2 _S 5 g / l is preferred The presence of a further sulfur-ZSauerötoff compound in the electrolyte according to the invention is not essential. However, Ea has often proven to be advantageous

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proved to use a further organic solvent / oxygen compound, as this often gives the electrolyte a greater tolerance to changes during the setting of the electroplating conditions. Such a sulfur / oxygen compound can consist of any of the compounds heretofore used in nickel-plating as a carrier brightener, although naphthalene-1,3> 6-trisulfonic acid, alone or in the form of its sodium salt, is generally preferred. Other organic Sohwefel- / oxygen compounds that may be given special mention in this context are sodium allyl sulfonate, sodium benzene sulfonate _r benzenesulfonamide and p-toluenesulfonamide. Such an additional organic sulfur / oxygen compound can be added in commonly used amounts, for example aromatic sulfonates in amounts of 2-20 g / l and sulfonamides in amounts of 0.5-3 g / l.

The operating conditions for electrolytes according to the invention generally correspond to the conditions usually used for electrolytes based on the nickel salts mentioned. As a rule, the pH of the electrolyte should be between 2.5 and 5.5, preferably between 3.5 and 5.0. The operating temperature of the electrolyte should zwisohen 40 and 70 ⁰ C, preferably between 50 and 60 ⁰ O. The electrolyte can be operated at a wide variety of current densities, for example at a current density of about 0.002 to 0.108 amps / cm (2-100 amps / sq Jt) . The workpiece held as a cathode can be moved in the electrolyte during operation. On the other hand, the electrolyte can also be moved, for example by blowing air.

The galvanic Niokel coverings according to the invention can either as a solo or as a basic

009886/1935

a galvanic chrome coating is then applied.

The following examples are intended to illustrate the invention in more detail.

example 1

The following additives were incorporated into a highly concentrated nickel chloride electrolyte containing 200 grams of nickel chloride, 50 grams of nickel sulfate and 40 grams of boric acid per liter: Condensate of 2-butyn-1 _t 4-diol (1 mol) and ethylene oxide (2 mol) 0.175 g / l

2-butyn-1,4-diol 0.089 g / l

Saccharin 2.5 g / l

Naphthalene trisulphonic acid (Na salt) 5.0 g / l The electrolyte with a pH of 4.5 was used for experimental purposes at a temperature of 55 G in a Hull cell used. At current densities from about 0.002 to

0.108 amps / cm (2 - 100 amps / sq.ft.) Was the galvanic Coating bright and even, i.e. smooth. The degree of smoothing at

a current density of about 0.043 amps / cm (40 amps / sq.ft.) was $ 70 (measured as the percent improvement in surface roughness after the deposition of 0.0127 mm (0.0005 inch) thickness of nickel on a surface an initial roughness between 25 and 30 CLA- (CeA ¹ Cr β Line Average—), these values being defined and measured in accordance with British Standard Specification 1134). A corresponding degree of smoothness was achieved if the naphthalene trisulphonic acid was omitted.

Example 2

Example 1 was repeated using different amounts of the two acetylene compounds. The overall

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aoetylene content was increased to up to $ 50, but the ratio of condensate to oil alkynol was kept constant. The degree of smoothness stayed at 70-75 #, though. a slight deterioration in the pliability of the coating was observed.

Example 3

Example 1 was repeated, with the exception that the condensate concentration was 0.275 g / l and the 2-butyn-1,4-diol concentration was 0.05 g / l. at Using the two acetylene compounds in this weight ratio of 5.5: 1 retained the degree of smoothness at around $ 70. There was little tendency to be educated to observe holey coatings. However, this disappeared when the ratio was lowered to 4: 1.

Example 4

A Watt type electrolyte was prepared from each liter of 250 grams of nickel sulfate, 50 grams of nickel chloride and 40 grams of boric acid. Then, as described in Example 1, brighteners were added and then the electrolyte was ^{tested at a pH of 4.5 and a temperature of 55 °} C. in a Hull cell. At current densities between about 0.002 and 0.194 amps * re / cm (2-180 amps / sq.ft.), Bare coatings with a degree of smoothness of $ 70-75 were obtained.

Claim

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Claims (1)

Claims Aqueous electrolytes for nickel-plating with a content of at least one nickel (II) salt, at least one acetylene compound and at least one organic sulfur / oxygen compound, characterized in that they contain 0.1 to 1.0 grams of a mixture of acetylene compounds per liter, including both an oC-hydroxyacetylene compound, preferably 2-butyn-1,4-diol, and an alkylene oxide condensation product of an oC-hydroxyacetylene compound in a condensate to oC-hydroxyacetylene compound weight Λ ratio of 1.5? 1 to 7 J 1, preferably from 2 t 1 to 5.5 s 1 and furthermore 1.0 to 5 »0 grams per liter optionally substituted / contain saccharin. 2 _# electrolysis according to claim 1, characterized in that in addition to 130-350 grams, preferably 150-200 grams of nickel (11) chloride, they contain 50-225 grams of nickel (II) sulfate and 20 to 45 grams of boric acid per liter. 3. Electrolytes naoh claim 1 or 2, daduroh marked; λ indicates that the condensate 1 to 4 oxyethylene! "has units and is preferably prepared from 2-butyn-1,4-diol. 4. Electrolytes naoh one or more of the preceding claims, daduroh geke.nnzeiohnet that they have a second organic sulfur / oxygen compound, preferably naphtha-1,3,6-tr isulfonic acid β or a salt thereof. 009886/1936