铬镀层及其阴极化修饰镀层的钝化行为

用电沉积方法在ＡＩＳＩ ４３０不锈钢上得到铬、铬钯交替镀层和铬钯复合镀层，凭借钯的阴极修饰效应，含钯的铬镀层在除氧的非氧化性酸中具有自钝化能力，极化曲线和阻抗频谱测定表明，在相庆铬镀层处于活化－钝化的电位区间，含钯镀层都表现出净阴极电流；活化溶解与钝化过程随电位的相对发展变化可由低频段容抗圈的演变来推定，铬钯复合镀层具有更大的钝化膜阻抗。

PASSIVATION BEHAVIOUR OF CHROMIUM PLATING FILM AND ITS CATHODICALLY MODIFIED SPECIES

Electrolytic plating chromium plain film, alternately multi-layered palladium alld chromium plating film and palladium-containing chromium composite plating film on AISI 430 stainless steel were compared for the purpose of showing the effect of palladium as cathodic modification element in chromium plating film. The electrochemical behaviour of the above coatillgs was examined in comparison to 430SS substrate by voltammetry and impedance spectroscopy. At potentials corresponding to the active-passive transition for chromium film, net cathodic current was measured oil those palladium-containing platings. While chromium may stably exist in either the passive or active state, small amoullt additioll of palladium significantly increases the corrosion resistance of chromium plating in deaerated 5% and 20% sulfuric acid solutions in consequence of spontaneous passivation. The tendency is more propounced for the composite coating. The capacitive circle which appears in the low frequency range of IHz-0.01Hi on the impedance diagrams is considered as ajssociated with the passivation process.