The Influence of Tungsten on the Pitting of Aluminum Films

Abstract

Many of the alloying additions responsible for the corrosion resistance of stainless steels can also be used to enhance the passivity of aluminum, provided that these elements remain in solid solution in the alloy. Passivity enhancing elements such as Cr, Mo, Ta, Zr, and W typically exhibit very low solubility limits in aluminum, below 1 atomic percent, and at these concentrations exert little influence on corrosion behavior. However, these solubility limits can be increased with a concomitant enhancement in corrosion performance if the alloys are produced using a rapid solidification process. One such process is co-sputter deposition of two metals, such as Al and W, simultaneously to form a binary alloy of W in solid solution with Al. Co-sputter deposition is routinely used to produce compound semiconductor films. The authors report on shifts in pitting potentials and on the effect of a transition element (W) on pitting resistance of Al.