Combining roles of mercapto-based corrosion inhibitor and inorganic layer for high corrosion resistance of commercial Mg alloy
T. Suhartono(a) , M. P. Kamil(ab*) , Y. G. Ko(a*)

a) Materials Electrochemistry Group, School of Materials Science and Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea
b) National Research and Innovation Agency (BRIN), DKI Jakarta 10340, Indonesia

Abstract

Despite the growing interest in dealing with how to enhance corrosion properties of active metallic materials, a role of organic corrosion inhibitor has remained less understood with respect to the formation of hybrid architecture as well as the decrease in corrosion rate that might result in the electrochemical stability. To this end, the present work used three distinctive mercapto-benzazole (MB) compounds working as corrosion inhibitor, such as 2-mercaptobenzoxazole (MBO), 2-mercaptobenzothiazole (MBT), and 2-mercaptobenzimidazole (MBI) in a bid to understand how the geometrical structure arising from O, S, and N atoms affected the interaction toward defective inorganic layer. According to density functional theory calculations, MB compounds would be fairly adsorbed on inorganic surface through S atom at the mercapto-site. Moreover, the presence of two donor atoms close to the mercapto-site would reduce the adsorption tendency, which agreed well with the result of electrochemical measurements. For all cases used in this study, the reliable corrosion stability was provided for at least 36 h due to the coexistence of organic inhibitor and oxide-based coating. More interestingly, the corrosion properties of MBI was higher than the other candidates. This was attributed mainly to the fact that the whole formation of the ^grass-like^ hybrid structure with a uniform distribution occurred successfully as a result of molecular self-assembly triggered by an organic-inorganic interaction. The nucleation and growth of hybrid structure were discussed in relation to adsorption calculation and microstructural observation by considering the singular role of the mercapto-part in MB compounds responsible for extraordinary corrosion properties of Mg-based alloys.

Keywords: Corrosion inhibitor- Mercapto-benzazole compound- Organic-inorganic interaction- Hybrid structure- Density functional theory- Electrochemistry.

Topic: Industrial and Engineering Chemistry