Passivity and Corrosion Resistance of Titanium and Its Alloys

A brief review is given of possible ways to increase corrosion resistance of titanium in acids proceeding from analysis of its electrochemical characteristics and passive state stability. Rational ways of alloying titanium for acid resistance are indicated. Experiments include titanium alloys with palladium, chromium, and molybdenum in solutions of sulfuric and hydrochloric acids. It is established that the greatest increase of corrosion resistance is obtained when titanium is alloyed with cathodic additions capable of shifting the corrosion potential of alloys in the noble direction (as, for instance, by palladium and other noble metals) and simultaneously by metals which increase the tendency of titanium to passivate or which diminish the degree of its thermodynamic instability (as is the case with chromium, molybdenum, zirconium, and possibly tungsten).