Comparison of Electrochemical Properties of CrSiCN, CrBCN, and CrSiBCN Films in Acidic and Alkaline Artificial Sweat

摘要

Wearable device shell materials will inevitably be corroded by human sweat during use. The purpose of this study is to construct three composite films of CrSiCN, CrBCN and CrSiBCN with corrosion resistance on silicon wafers and 316L stainless steel substrates by using closed-field unbalanced magnetron sputtering technology as protective films, to protect the corrosion of shell materials. The electrochemical behavior of Si and B element doped films under acidic and alkaline artificial sweat was studied by electrochemical noise, AC impedance and potentiodynamic polarization electrochemical measurement techniques, and the microstructural changes of the films were characterized by scanning electron microscopy, x-ray diffraction and laser Raman spectroscopy. Electrochemical test results show that the films exhibit a higher corrosion rate compared to alkaline artificial sweat due to the higher concentration of chloride ions, hydrogen ions, and lactic acid corrosive ions in acidic artificial sweat. The results also demonstrated that the inhibitory effect of a high concentration of hydrogen ions in acidic artificial sweat resulted in a relatively low surface oxygen content, whereas the doping of the boron element promoted the growth of passive film on the coating surface, thereby decreasing the corrosion rate of CrBCN film in acidic sweat. Furthermore, the high concentration of hydroxyl ions in alkaline artificial sweat accelerates the electrochemical reactions of passive film growth (mainly chromium oxides and hydroxides), hence enhancing the corrosion resistance of the CrSiCN film with its denser and smoother surface.