Galvanic Corrosion Behavior of Titanium and Zirconium in Sulfuric Acid Solutions

Abstract

Aluminum alloys are the anodic members of titanium‐aluminum alloy couples in dilute sulfuric acid solutions in the presence of air. In stronger acid solutions, particularly when air is absent, aluminum alloys are anodic only at the beginning of the immersion period. After an induction period titanium becomes anodic. Aluminum alloys are always anodic in zirconium‐aluminum alloy couples immersed in sulfuric acid solutions. The rate of galvanic attack increases with the supply of air. The direction of flow of the galvanic current is always in agreement with the relative values for the electrode potentials of the single metal specimens. Little, if any, galvanic corrosion occurs in couples of titanium or zirconium with stainless steel, although there are generally sizeable differences of potential between single specimens of these metals. In solutions in which single specimens of titanium are inert and cathodic with respect to aluminum alloys, contact with these alloys may cause titanium to corrode. This is attributed to activation of titanium surfaces by the hydrogen evolved. Contact with stainless steel in solutions in which titanium is the anodic member of the couple results in marked decreases in corrosion rates of titanium because of anodic polarization of titanium surfaces.