Corrosion behaviour of Ti_3Al and Ti_3Al-11 at.% Nb intermetallics

摘要

The corrosion behaviour of Ti_3Al and Ti_3Al-11 at.% Nb was studied and compared to Ti with salt fog spray test and electrochemical methods in NaCl, HCl, H_2SO_4 and HNO_3 solutions. The corrosion mechanism of Ti_3Al in salt fog is suggested to be the dissolution of Al and oxidation of Ti. Polarisation curves of Ti_3Al and Ti_2Al-11Nb in 0.5N NaCl and 1.0N HCl solutions showed passive and pitting behaviour. However, Ti_3Al-11Nb showed higher pitting potentials than Ti_3Al, especially in 1.0N HCl solution. Polarisation of Ti, Ti_3Al and Ti_3Al-11Nb in 1.0N H_2SO_4 solution demonstrated passive behaviour. In 1.0N HNO_3 solution, these intermetallics exhibited passive behaviour but without an active region. The addition of 11 at.% Nb to Ti_3Al improves the corrosion and pitting resistance in some acid and neutral chloride solutions. It is believed that the improvement is related to the specific microstructure and composition containing Nb with a high corrosion resistance.