Search

A novel electroless Ni Plating bath using Ti (III) ions as reluctant was proposed. In an industrial application of this plating bath, stability of the plating bath and plating rate are particularly important. Effects of plating bath components on Ni deposition rate onto Urethane foam or copper sheet were investigated, elucidating that Ni (II) ions, nitrilotriacetic acid and ammonium hydroxide concentration were important factors to control Ni deposition rate. Purity of Ni film reduced with Ti (III) ions was very high exceeding 99.9%.

Direct electroless silver plating on copper metal from a succinimide complex bath using imidazole as the reducing agent was examined. Though the electroless silver plating from this bath is essentially an autocatalytic deposition, there is a problem in the properties and adhesion of the plated film because of the substitution deposition of silver due to the dissolution of the base copper metal that occurs during the first stage of plating. By adding glyoxylic acid, which is catalytically reacted on the copper surface to emit electrons, as the second reducing agent, the substitution deposition of silver was suppressed, the surface condition became dense and the adhesion was improved. It has been determined that the mixed potential theory can be applied to this reaction based on the result of the local polarization curve measurement.

Tin-zinc alloys of low zinc content are believed to have high corrosion resistance when they are used for protective films on steel surface. This paper describes the following studies: an optimum composition for protective films was selected by electrochemical measurements of the cast alloys; and, zincate-stannate baths and gluconate baths were investigated to obtain such alloy deposits from baths free from cyanides and fluorides. The following results were obtained: (1) The static potential of tinzinc alloys was base enough to act as a sacrificial film for steel, and the potential of an alloy containin more than about 10% of zinc showed almost the same value as that of single zinc. (2) The anodic dissolution in NaCl solution and the formation of white precipitate on the alloy surface in a salt spray test more readily occurred with the increase in zinc content of the alloy. (3) It was difficult to obtain alloy deposits of lower zinc content from zincate-stannate baths under normal plating conditions. (4) A semi-bright zinc alloy deposit of lower zinc content was obtained from the bath containing 0.25mol/l of metal and 0.50mol/l of Na-gluconate with an additive such as 0.25mol/l of triethanolamine, 2.5-5g/l of polyethyleneglycolnonylphenylether (PEGNPE), 0.2-1g/l of peptone, and 0.04-0.06g/l of o-vanillin at pH=5. It was observed that a deposit of fine luster was apt to be obtained at a composition of nearly equi-molecular ratio between tin and zinc. (5) It was further observed that a deposit of highest zinc content was obtained from gluconate baths containing 20 and 35% of zinc at pH=5, and the zinc content of deposit was almost equal to that of the bath when the plating was conducted at a current density of 1-2Amp/dm2.