Mechanisms of Passivity of Nonequilibrium Al‐W Alloys

Sputter‐deposited Al‐W alloys exhibit considerably enhanced resistance to pitting corrosion over a range of pHs extending from pH 0 to 9.6. Surface analysis showed that although very little oxidized W is found in the passive film at near‐neutral pHs, at pH 3 there are comparable amounts of oxidized W and Al. A review of the different mechanisms proposed to explain the passivity of this class of alloys suggests that the pitting resistance of Al‐W is likely to result from inhibition and repassivation of pits due to the stability of oxidized W in low‐pH environments as described by the solute‐rich interphase model (SRIM).