Patent GB-1323756-A (GB)
Title: Electroplating bath
IPC: C25D15/02
Filed: 1970-08-13
Abstract: 1323756 Electro-plating with platinum group metal; anode for electrolysis of alkali metal chloride solution PPG INDUSTRIES INC 13 Aug 1970 [14 Aug 1969] 38976/70 Heading C7B An electro-plating bath for preparing an anode comprises an "organic based solution" including (a) a platinum group metal compound, (b) a  "highly ionizable electrolyte" and (c) an organic material, the organic material being capable of being decomposed to produce carbon without substantial volatilization of the organic material. "Organic based solution" means a solution in which the solvent (if only one is employed), or the solvent which is the major portion of the solution by volume, is of an organic nature, "Highly ionizable electrolyte" means an electrolyte of such a nature and present in such an amount that the electroplating bath containing it has a conductivity of at least 0À01 mho. The organic material (c) may serve as the organic solvent or may be soluble or suspendible therein. The anode is prepared by electro-depositing from the bath a coating including the platinum group metal and the organic material and thereafter decomposing the latter, e.g. by thermal or chemical means, so as to produce a coating comprising the metal and carbon. Such an anode, e.g. with the coating on Ti, Ta, Zr, Nb or an alloy thereof, can be used as anode in the electrolysis of aqueous alkali metal chloride, e.g. to produce (i) alkali metal hydroxide and chlorine, (ii) chlorate or (iii) hypochlorite in appropriate cells of the diaphragm, mercury cathode or diaphragmless types. Specified constituents of the electro-plating bath are an organic solvent of ethyl, propyl or butyl alcohol, ethyl methyl ketone dioxane, dimethyl sulphoxide, dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidine, furfural, acetylacetone polyethylene glycol, phenol or a mixture of glycol and glycerine; a platinum group metal compound (a) of chloroplatinic acid or platinum nitrate optionally together with a compound of another platinum group metal; an electrolyte (b) of H 2 SO 4 , HCl, CH 3  COOH or a mixture of acetonitrile and tetra-n-butyl ammonium bromide; and an organic material (c) of toluene, tetraethyl orthosilicate or butyl alcohol. The bath may also contain Ti compounds. The electroplating may be at 10-70‹C. using 2-50 amps/sq ft. During the electro-plating the electric potential may be reversed periodically for a short time. After the electro-plating the electrode may be heated at between 200 and 700‹C. All the Examples disclose electro-plating on to cleaned Ti from baths containing C 2 H 5 OH, chloroplatinic acid, H 2 SO 4  and toluene. In addition the baths in the following Examples include I and III acetone, III and IV rhoduim trichloride and V tetraethyl orthosilicate. Before the electro-plating, the Ti was cleared and etched by treating it with (a) detergent, (b) a solution of HF + HCl, (c) HCl and (d) acetone. A chlorine diaphragm cell used for testing anodes comprises a Pyrex (Trade Mark) pipe 6 inches in diameter having therein iron mesh screens in the form of an enclosed tube 2 inches in diameter covered with an asbestos paper diaphragm with test anodes spaced there around.