Effect of Potential on Hydrogen Evolution during Pitting of Aluminum

Abstract:

Effect of potential on hydrogen evolution during simulated pitting of aluminum has been investigated. Aluminum wire in 1.0 mm diameter was mounted in resin, immersed in 0.6 kmol^.m^-3 NaCl solution and anodically dissolved in axial direction by applying a constant potential from-0.6 to-0.1 V_Ag/AgCl for 86.4 ks. In addition, a resistance of the solution in the crevice of the resin where the aluminum wire corroded was simultaneously measured by superimposing high-frequency alternating potential (E_p-p=10 mV) to the main potential. As higher main potential was applied, the corrosion depth increased. Hydrogen evolved at the corroded site although the anodic potentials were applied. The amount of hydrogen evolution increased as higher main potential was applied to the wire. An interfacial potential (E_int) at just the wire surface was calculated from applied main potential (E_app), solution resistance (R_sol) and current (I) as E_int = E_app - I^.R_sol. The interfacial potential was about-0.7 to-1.0 V_Ag/AgCl, and became lower as the higher main potential was applied. The lower interfacial potential may cause hydrogen evolution in this case.