THE CORROSION BEHAVIOR OF MO-AL, CR-AL AND CR-MO-AL SURFACE ALLOYS PRODUCED BY ION-BEAM MIXING AND ION-IMPLANTATION

The corrosion behavior of Mo-Al, Cr-Al and Cr-Mo-Al surface alloys produced by ion implantation and ion beam mixing was examined in de-aerated, 0.1 M NaCl. The polarization behavior of the ion implanted samples was similar to that of Al, and the pitting potentials of the ion implanted samples were 115-155 mV higher than that of Al. From the standpoint of the pH of zero charge model, this behavior would be explained by the presence of the implanted cations in the stable oxide lattice. There was incomplete mixing of the coating and substrate for the ion beam mixed samples, and the mixed elements remained almost entirely in the metallic state so that the desired mixed oxide films were not formed. Ion beam mixing did impart additional stability compared to as-deposited samples because the mixing process produced more compact, less porous coatings.