不锈钢表面Cr-Pd合金电沉积及镀层在强还原性介质中的耐蚀性

通过选择络合剂、缓冲剂及采用方波脉冲电流和优化电镀工艺, 在酸性镀液中实现了Cr-Pd共镀, 并在不锈钢表面制备出均匀致密且与基体结合良好的Cr-Pd合金镀层. 通过改变镀液中铬盐和钯盐的相对含量, 可以大范围改变镀层成分. Cr-Pd合金镀层可显著提高不锈钢在高温还原性腐蚀介质中的耐蚀性, 在沸腾的20%(质量分数)H₂SO₄溶液中, Cr-Pd合金镀层使316L不锈钢的腐蚀速率降低了4个数量级以上. 镀层中的Cr和Pd对致钝具有协同促进作用, 当镀层中含有2.5%Pd(质量分数)时即具有明显的促进钝化效果, 含33.3%Pd镀层对不锈钢的保护效果与纯Pd镀层相当.

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.