低濃度クロムメッキ液からのクロムメッキに及ぼす金属カチオンの影響と作用

抄録

Effects of metallic contaminants, such as Na, Mg, Zn, Cd, Ni, Cu, Fe, Cr, Hg, In, and Tl in low concentration chromium plating bath (CrO₃ 50g/l, H₂SO₄ 0.5g/l and Na₂SiF₆ 0.5g/l) were investigated. 1) An addition of metal oxides or hydroxides of 0.15g. eq/l resulted in the burnt deposits at high current densities and by the further addition of metals of 0.25g. eq/l and 0.35g. eq/l no chromium deposit was obtained at current densities of above 50A/dm² and 15A/dm², respectively. When the amount of metals was increased to 0.50g. eq/l complete loss of chromium plating was observed independent of the metal species studied. 2) Metals of I B, II B and III B groups in the periodic table were found to improve the covering power of chromium plating and it is noteworthy that these metals have the high hydrogen overpotentials. 3) When an addition of NiSO₄⋅7H₂O or CoSO₄⋅7H₂O was above 0.2g.eq/l, Ni-Cr or Co-Cr alloy was deposited in a reproducible manner.