Effect of SiO_3 /OH~- on plasma electrolytic oxidation of Ti-5Mo-4V-3Al

摘要

Plasma electrolyte oxidation (PEO) was utilized to produce thick Alms on titanium and Ti-5Mo-4V-3A1 alloys by immersing them in various solutions of Na_2SiO_3 and KOH with different concentrations to investigate the effect of SiO_3~(2-)/OH~- relations on the morphology and formed phases by utilizing SEM and XRD. Corrosion resistance is evaluated by open circuit potential (OCP) variation of samples in NaCl 3-5% and potentiodynamic polarization. The results show that the unstable film is formed by using more aggressive PEO electrolyte. By increasing this ratio, pore size varied from fine to coarse and the rate of corrosion decreased and OCP became more positive. The best protective film was formed in SiO_3~(2-) /OH~- ratio of 1.