GB886737A - Method of formulating chemical nickel plating bath - Google Patents

Abstract

A method of formulating an aqueous chemical nickel plating bath of the nickel cation-hypophosphite anion type containing an optimum amount of a stabiliser to prevent random decomposition thereof comprises (a) providing a number of samples of either a bath which contains no stabiliser or of a spent stabiliser-containing bath, (b) adding to said samples successively increasing numbers of increments of a stabiliser so as to produce a number of test baths respectively containing stabiliser concentrations successively increasing by NXp.p.m. thereof by weight, (c) providing a number of identical test specimens formed of the material of the work-pieces to be plated, (d) respectively plating said test specimens in said test baths at the same temperature and for the same time, (e) establishing from the plating results the plating rates of said test baths and the coating coverages thereof on the test specimens, (f) selecting as a group all of said test baths that have stabiliser concentrations in excess of that of the one thereof that is productive of the maximum plating rate, (g) selecting from said group the particular one of the test baths that is productive of both the highest plating rate and the most complete coating coverage, and (h) producing a production-bath by adding sufficient stabiliser to the bath from which the samples were originally taken to effect a stabiliser concentration therein that is 1/2 NXp.p.m. thereof by weight lower than that of said selected test bath. X should be of such value that the test bath containing 1Xp.p.m. thereof by weight is productive of a readily detectable variation in the normal plating rate of the bath from which the samples were taken, and N should be a value appropriate to the sensitivity range of the bath to the stabiliser. The stabiliser may comprise ions of a heavy metal (defined as lead, copper, bismuth, tin, tungsten, thorium, titanium, zinc, manganese, rhenium, selenium and tellurium), an inorganic thio-compound e.g. thiosulphate, or an organic thio-compound e.g. potassium ethyl xanthate. The method is applicable both to continuous plating systems, when the tests should be repeated periodically in order that the baths may be correctly regenerated, as well as to batch plating systems. Specifications 761,062, 761,567, 785,693, 785,694, 785,695, 785,696, 786,175, 821,762 and U.S.A. Specification 2,532,283 are referred to