Pitting behavior of Ti-15-3 titanium alloy with different surface in salt spray studied using electrochemical noise

Ti-15-3 titanium alloy has been widely used as a connecting material for aerospace structural parts. However, the non-uniform pitting caused by salt spray corrosion and the limitations of the conventional electrochemical techniques in predicting localized corrosion seriously prevent the practical application of Ti-15-3 alloy. Herein, the electrochemical noise based on discrete wavelet transform and Hilbert-Huang transform is employed for studying pitting corrosion of both the untreated and polished Ti-15-3 alloy under different neutral salt spray time. Combining with the further analysis of the electrochemical impedance spectroscopy, a complementary evaluation is used to analyze the effect of surface roughness on pitting corrosion behaviors of Ti-15-3 alloy systematically. It is found that pitting forms of both surface roughness electrodes exposed to different salt spray time are successfully distinguished, and the polished Ti-15-3 alloy shows better corrosion resistance. Microstructural characterization confirms the inferences from electrochemical noise analyses, the results indicate that the smooth surface of the polished Ti-15-3 alloy is less vulnerable to the coexistence of metastable pitting and the growth of stable pitting, and effectively improves the resistance to pitting corrosion of Ti-15-3 alloy. Furthermore, a possible mechanism for the triggering of pitting corrosion of Ti-15-3 alloy with different roughness in salt spray environment is proposed. This work will provide significant insights for rational design of Ti-15-3 alloy used in the tropical ocean facilities to avoid the attack of pitting corrosion.