LOCALIZED CORROSION BEHAVIOR OF ALUMINUM SURFACE ALLOYS PRODUCED BY ION-IMPLANTATION AND ION-BEAM MIXING

The pitting corrosion behavior of Mo-Al surface alloys produced by ion implantation and ion beam mixing was examined and compared with that of pure aluminum. The pitting potentials of various Mo-Al surface alloys produced by ion implantation were 0.140-0.175 V higher (more noble) than that of pure aluminum, indicating an increased resistance to pitting corrosion. Ion-beam-mixed surface alloys were prepared by either ion implanting or vapor depositing molybdenum on an aluminum substrate and then mixing with an inert or reactive element. The pitting potentials of the ion-beam-mixed samples were 0.100-0.650 V higher than the pitting potentials of aluminum or the Mo-Al surface alloys produced by ion implantation. The improvement in the pitting resistance of the Mo-Al surface alloys was related to the pH of zero charge model of passive film breakdown.