THE ELECTROCHEMICAL AND CORROSION BEHAVIOR OF TITANIUM AND ITS ALLOY (VT-9) IN PHOSPHORIC-ACID

Using potentiostatic techniques, cathodic and anodic polarization beha viour of titanium and its alloy (VT-9) have been investigated in diffe rent concentrations of H3PO4 solution at 30-degrees-C. Selected compos itions of the acid were taken to study the effect of temperature on th e metal and its alloy. They showed active/passive behaviour and a larg e passivity range of potential in different acid concentrations at dif ferent temperatures. The critical current density for passivity of the specimens was found to increase with increasing acid concentration an d temperature, but it decreased in 13 M phosphoric acid. The polarizat ion curves for Ti and VT-9 are alike in nature and the difference lies in the critical current density and passive current density which are higher for the alloy. SEM micrographs show the formation of a uniform passive surface on the metal and alloy which remained stable under ex posed condition for a long duration.