The Separation of Corrosion and Stress Effects in Stress Corrosion: Ti-Al-4V in Bromine-Methanol Solutions

The time to failure for stress corrosion of Ti-6Al-4V depends strongly on the extent of precorrosion. Corrosion without stress is initially just as effective in causing eventual failure as is corrosion with stress; only during the last 40% of the normal stress, corrosion life is stress critical in causing failure. Thus, only in this last stage can a stress corrosion process be said to occur. A general mechanism to account for this behavior is suggested, and a precorrosion susceptibility index is defined and used as a quantitative measure of the importance of stress at each stage of the total process leading to failure. The time to failure of Ti-6Al-4V in methanol-bromine solutions depends also on the extent of “aging” of the solution. The time to failure becomes shorter the longer the solution has been kept standing. This effect arises from the influence of the reaction products of bromine with methanol and water.