Impact of chloride and fluoride additions on surface reactivity and passivity of AM60 magnesium alloy in buffer solution

The electrochemical behaviour of AM60 alloy was investigated in pH 9.2 borate buffer solution including anions. The extent of surface reactivity and passivity is always a function of solution composition. Increasing Cl− concentration increases corrosion attack and decreases slightly surface film resistance (R1). Nevertheless, F− addition (>0.01 M) strongly passivates the surface, as it enhances formation of fluorinated film with superior corrosion resistance. At 0.01 M, fluoride induces surface activation and R1 decreases. Thus, fluoride can efficiently inhibit AM60 corrosion in chloride-containing solution, where it forms highly protective film with refined structure as confirmed by SEM and EDX examinations.

► Corrosion rate of AM60 and HE increase with increasing Cl− ion concentration. ► 0.01 M F− addition activates the surface compared to blank borate buffer solution. ► F− ion higher than 0.01 M remarkably increases surface passivity and decreases HE. ► SEM and EDX analyses show that fluoride forms highly protective fluorinated film. ► Fluoride can mitigate alloy corrosion in 0.1 M Cl− with more than 99% efficiency.