抄録
The passive films formed on Pb and Pb-Ag alloy (1 and 4wt% Ag) in 0.05 to 1M NaCl solutions have been studied by a linear potential sweeping method, potentiostatic and galvanostatic measurements. On the way to passive region of the E-I curves obtained by linear potential sweeping experiments, two distinct current peaks, peak 1 and peak 2, were observed at the concentration of 0.25M or above. An oxidation mechanism in term of peak 1 and peak 2 is proposed and discussed. It follows from comparison of Pb and Pb-Ag alloy that the use of Pb-4wt% Ag alloy induces a negative shift in oxygen evolution potential, but does a positive shift in film-dissolution potential. In addition, the alloy has a tendency to reduce slightly the retention current of passivation. The passive films, formed on both Pb and Pb-Ag alloy, have the structure which the inner layer is composed of PbO and PbO2, and the outer layer of PbCl2 and Pb(OH)Cl.
