Abstract: In order to improve corrosion resistance of pure titanium in strong acid solution,tantalum modified layer was formed on pure titanium surface by double glow plasma surface alloying technique.The corrosion resistances of the tantalum modified layer and pure titanium substrate in H2SO4 solution were investigated by immersion test and electrochemical techniques respectively,and the corrosion morphology was observed by scanning electron microscopy.The results indicate that the thickness of the tantalum modified layer was about 15 μm.The layer was composed of deposition layer and diffusion layer,which combined closely with substrate by metallurgy method.The tantalum element distributed gradiently.The annual corrosion rate of the modified layer was only 30% and 1.2% of pure titanium at the same condition in 10wt% and 40wt% H2SO4 solution,and the rate of the modified layer was still small in 75wt% H2SO4 solution,which was only 0.008 8 mm·a-1.After the pure titanium substrate was corroded in concentrated sulfuric acid for 120 h,its corrosion surface already had a lot of corrosion pits,while there was no significant difference on the surface of the tantalum modified layer before and after corroded.The whole modified layer was still integrated and compact.