Alkaline Platinum Electroforming Bath Using Hexahydroxoplatinate

We studied the influence of bath composition, operating conditions, and impurities on a platinum electroforming bath using hexahydroxoplatinate salt. The effect of bath temperature on deposite were studied using a platinum concentration of 13g/L and a pH of 135. Crack-free deposits resulted at temperatures of exceeding 85°C. At a platinum concentration of 26g/L, the pH was 13.5 and temperature 90°C, yielding a 60μm platinum foil. The platinum content of deposits exceeded 99.9%, which contained palladium, rhodium, gold, silver, copper, and iron impurities. X-ray diffraction imaging showed a strong (200) orientation on ductile deposits. Deposit hardness exceeded 300Hv and hardness decreased in heat treatment exceeding 600°C. The bath thus is easily influenced by impurities. Calcium is thought to be a deterioration agent. The presence of calcium, strontium or barium made the deposit less ductile and brighter. The influence of alkaline earth metals was eliminated through electrolysis, coprecipitation with magnesium hydroxide, and absorption to chelate resin.