Anodic Polarization and Localized Corrosion Behavior of Amorphous Ni35Fe30Cr15 P 14 B 6 in Near‐Neutral and Acidic Chloride Solutions

Abstract

The anodic polarization and localized corrosion behavior of amorphous were obtained in 0.02, 0.2, 0.6, and 2.0M chloride ion solutions of pH 6.6, 4.0, and 1.0. Regardless of the hydrogen ion and chloride ion concentrations of the solution, the alloy remained immune to pitting corrosion. The passive corrosion current density was insensitive to changes in chloride ion concentration. The passive corrosion current density was independent of solutionpH between pH 6.6 and 4.0. Decreasing the pH from 4.0 to 1.0 resulted in a threefold increase in passive corrosion current density. The alloy was susceptible to crevice corrosion. Plastic deformation affected neither the passive corrosion current density nor the pitting corrosion resistance. Severe cold‐rolling resulted in cracking and crevice corrosion occurred at cracks. The results suggest that the great resistance of amorphous to pitting corrosion is due to its resistance to pit nucleation which can be attributed to its high degree of chemical homogeneity and lack of inclusions. The as‐received amorphous ribbon is highly chemically inhomogeneous. Auger electron spectroscopy indicates the top surface of the ribbon is greatly enriched with chromium and both surfaces are depleted of phosphorus. Anodic polarization measurements suggest the top surface is covered with a film.