ELECTROPLATING OF Cr-Pd ALLOY ON 316L STAINLESS STEEL AND ITS CORROSION RESISFANCE IN THE STRONG REDUCING MEDIUMS

By selecting complexing agent and the buffer agent, using square wave pulsed currents and optimizing electroplating process, the chromium-palladium alloy films were deposited on 316L stainless steel in acidic solution. By appropriate design for the plating bath composition and pulse electroplating, Cr-Pd alloy films were deposited on 316L stainless steel. The films were compact and homogeneous with good adherence to the substrate. By adjusting the composition of the plating bath, the ratio of Cr/Pd could be changed in a large range. The Cr-Pd films significantly improved corrosion resistance of 316L stainless steel in strong reducing mediums. In boiling 20% (mass fraction) H2SO4 solution, corrosion rates of the Cr-Pd plated samples were about four orders of magnitude lower than that of the original 316L stainless steel samples. A synergism effect was observed for Cr and Pd on passivation of stainless steel. When there was only 2.5%Pd (mass fraction) in the Cr-Pd film, corrosion resistance of the sample was obviously improved. The protection effect of Cr-33.3%Pd film was similar to that of pure Pd film on stainless steel.