Effect of sodium hexa-meta phosphate as pore-sealing agent on the corrosion performance of Al-Zn coating deposited by twin-wire arc thermal spray process in 3.5 wt.% NaCl solution

3.5 중량% NaCl 용액에서 쌍선 아크 용사 공정으로 증착된 Al-Zn 코팅의 부식 성능에 대한 기공 밀봉제로서의 헥사메타인산나트륨의 영향

Al and Zn are used to protect the steel structures from corrosion. In the present studies, 15Al-85Zn alloy wires has been used for the deposition of coating by arc thermal spray process. Moreover, this process of coating exhibited severe defects formation, therefore, this coating was post-treated with different concentrations i.e. 0.05, 0.1 and 0.5M sodium hexa meta phosphate (Na6[(PO3)6]: SHMP) to fill to defects of deposited coatings and assessed their corrosion resistance in 3.5 wt.% NaCl solution with exposure periods. After the treatment, the porosity of the coating reduced significantly by formation of composite oxide films onto the coating surface. Initially, 0.5 M SHMP treated coating exhibited highest in total impedance due to significant reduction of porosity but once the exposure periods are extended, the composite oxides are dissolved, thus, total impedance is decreased.