Corrosion Behavior of the Open Surface of Commercially Pure Titanium in NaCl-HCl Solutions

Abstract

Passivity and its breakdown on titanium have been studied in NaCl solutions of various concentrations, pH’s and temperatures. The corrosion rate of commercially pure titanium depends on pH and temperature of the solution. Depassivation pH where active dissolution begins to occur with decreasing pH is found from the relationship between pH and polarization resistance at constant temperatures. The concentration of Cl⁻ does not affect the breakdown of passive film on titanium unless pH decreases. The titanium hydride layer is formed on the titanium surface when the active dissolution reaction takes place. Titanium dissolves in the solution to produce Ti³⁺ through the titanium hydride layer. The investigation of the corrosion behavior of titanium in these solutions of high concentrations of chloride and hydrogen ions is useful for a better understanding of crevice corrosion of titanium.