Formation of protective conversion coating on Mg surface by inorganic inhibitor

In the present work, NaH2PO4 was proved to be a highly efficient inhibitor to enhance barrier properties of the corrosion product layer on AM50 Mg alloy. Formation of typical porous and non-protective Mg(OH)2 based corrosion product layer is suppressed after addition of corrosion inhibitor in 3.5 wt% NaCl solution, while a dense and protective chemical conversion coating appears on the active Mg surface. The phase composition of the conversion-like coating is mainly composed of MgHPO4 and Mg3(PO4)2, leading to significantly enhanced corrosion and tribocorrosion performance compared to corrosion produced layer formed in 3.5 wt% NaCl solution.

Automated summary

The addition of NaH2PO4 inhibits the formation of the porous and non-protective Mg(OH)2 corrosion product layer in 3.5 wt% NaCl solution, and instead forms a dense and protective chemical conversion coating on the active Mg surface. The conversion-like coating consists mainly of MgHPO4 and Mg3(PO4)2, resulting in significantly improved corrosion and tribocorrosion performance compared to the corrosion product layer formed in 3.5 wt% NaCl solution.