CS201412B1 - Electrolyt for cathodic production of zinc-tungsten alloys - Google Patents

Abstract

An aqueous electroplating solution comprises nickel sulphosalicylate in a 0.1 to 1.05 M concentration, and a tungsten salt in a 0.001 to 0.1 M concentration. The solution may include nickel bromide in 0.01 to 0.2 M concentration, and disodium lauric sulphate surfactant in 0.002 to 0.04 M concentration. The electrolyte results in low stress platings.

Description

The present invention relates to an electrolyte for cathodic deposition of nickel-tungsten alloys.

Electrolytically deposited nickel-tungsten alloys have markedly improved properties over pure electrolytic nickel. It is especially hardness and resistance to oxidation at higher temperatures. For this reason, a number of procedures for their elimination have been described. The electrolytes used so far are mostly based on nickel sulphate as an essential component of the electrolyte, with the addition of sodium or nickel chloride, to improve the solubility of the anodes and acid. Tungsten is added in the form of sodium tungstate. In order to keep the tungsten in solution, complexing agents such as citric or tartaric acid salts must be added. The disadvantage of these processes is that the deposited layers usually have a high value of internal stresses, which limits and decreases their applicability, especially when applying thick layers. For this reason, electrolytes generally only work at high temperatures around 90 ° C, which in practice brings further operational and technological difficulties.

The electrolyte according to the invention for cathodic deposition of nickel-tungsten alloys eliminates these disadvantages. The electrolyte comprises an aqueous solution of nickel sulfosalicylate at a concentration of 0.1 to 1.05 M and a tungsten salt, for example sodium tungstate at a concentration of 0.001 to 0.1 M. In another aspect of the invention, the electrolyte comprises a halide, for example, nickel bromide at a concentration of 0.01 to 0.2 M. According to the last feature, the electrolyte contains ionic A / or non-ionic

201 412

201 412, e.g. sodium lauryl sulphate, at a concentration of from 0.002 to 0.04 M.

An essential constituent of the electrolyte nec is nickel sulphosalieylan. A suitable halognide may be used to improve the dissolution of the anodes. Woofram is also added to the solution in the form of sodium tungstate.

Because of the complex anionic property of the basic anion, in the case of lower tungsten contents, it is not necessary to add corticostexing agents, which is another advantage of the electrolyte. The electrolyte operates at a very low level of internal stresses already at 40 ° C and can also be used up to 90 ° C. The current densities sn used range from 1 to 15 n

A.dm ~ ·, according to the conditions of electrolysis. Cathodic current efficiencies not greater than 90% at pH values greater than 2.9. Exemplary embodiments of the electrolytes of the present invention are exemplified in Examples 1-3.

Example 1 ’

The electrolyte for the cathodic deposition of tungsten-nickel alloys contained nickel sulfosalicylate at a concentration of 0.8 M and sodium tungstate at a concentration of 0.01 M.

The resulting layer contained 2.65% tungsten hrnootnotních · mmla and inner pnuu ^ i 66.7 MPa jnjí oikrotvrdost was 518 HM when the diameter ZČ three bath pH was 4, a cathodic ^and an Prou ^d oic ^h ustota was' 5 ^{A. d} m ^"2 and the bath temperature ^{of b} YLA 50 ° C.

Example 2

The electrolyte for the cathodic deposition of nickel-tungsten alloys using halogene contains nickel sulfosalicylate at a concentration of 0.75 M, nickel bromide at a concentration of 0.05 M and sodium tungstate at a concentration of 0.01 M.

the foitoia wicker frustota was ^{1 A. d} ^ m ^"2 ^ -tnplo the l.ázně was 50 ° C and JNJ ^{s pH} was 4. The deposited layer had a content of 3% wolfrmiu hmoonootní, internal stress of 78.1 MPa and a micro-directed rotvrdost was 735 HM. 'i

Example 3

An electrolyte for cathodic deposition of nickel-tungsten alloys containing a mixture of sulfosalicylan. · Nickel (II) in 0.75 M, nickel (II) bromide in a concentration of 0.05 · M, sodium tungsten in -θ ^ ο ^ Ογηο! 0.03 M sodium lruryl sulphate in the concentrate. 0,004'M. ;

The deposited layer mmla Content 'Woofremu 4.65% hmotnosních, internal stress was 178 MPa r a mikrotvrtost Tyl · 600 · ^HM totodická Prou ^d s ^{s h} ustota was 10 A.dm ^{2 P} M A ^ of r was 3,2 jnjí temperature 68 ° C.

Claims (3)

An electrolyte for the cathodic deposition of nickel-tungsten alloys, characterized in that it consists of an aqueous solution of nickel sulphosalicylate in a concentration of from 0.1 to 1.05 M and a tungsten salt, for example sodium tungstate in a concentration of from 0 to 001 to 0; 1 M · 2. Electrolyte according to claim 1, characterized in that it contains a halide, for example nickel bromide, in a concentration of from 0.01 to 0.2 M. 3. The electrolyte according to claim 1, characterized in that it contains ionic and / or non-ionic sodium lauryl sulphate, for example, in a concentration of from 0.002 to 0.04 M.