Abstract
In the previous paper the authors reported that compound layers of nitrdied titanium showed high corrosion resistance in hydrochloric and sulfulic acids. In strongly oxidizing nitric acids, however, the nitrided titanium is assumed to exhibit a different behavior because the reduction of nitrate ions will occur as a catholic reaction. The present paper aims to clarify the corrosion behavior of nitrided titanium in nitric acid. The corrosion rate and corrosion potential of the nitrided titanium were measured in nitric acid. Potentiostatic polarization measurements were also performed in hydrochloric acid after a certain time of corrosion in nitric acid. Electron diffraction method was applied to examine the change in composition of the surface layer with time of corrosion in nitric acid. After dissolution of the outer layer of nitrided titanium in nitric acid, the corrosion rate decreased and passivation occurred on a solid solution layer.
