Passivity and Pitting of Al, Ni, Ti, and Stainless Steel in CH 3 OH + H 2 SO 4

Abstract

The polarization behavior of Ti and Ti alloys, Ni, Al 6061, stainless steel Type 304, Fe, Cu, and Pt has been studied in methanolic solutions containing sulfuric acid. As in solutions of , pitting occurs on Ti alloys in solutions of . Addition of leads to a broad region of passivation. Addition of does not effect the polarization curves of nickel in the cathodic region and the region of active dissolution. The water addition leads, however, to passivation on further anodic polarization. Pitting is observed after polarization in the transpassive region. Iron cannot be made passive in . Stainless steel is readily passivated in without addition of water, but pitting is observed after polarization in the transpassive region. Al 6061 suffers from severe pitting when polarized anodically in free of water additions. Copper shows no active‐passive transition in solutions. Experiments with Pt show that methanol is decomposed at potentials higher than +1.0V vs. SCE. Contrary to susceptibility in aqueous solutions containing halides, Ti is more susceptible to pitting in than Al 6061, Ni, and stainless steel 304.