Influence of corrosion products on the corrosion behaviors of Mg-Nd-Zn alloys

Abstract

The effect of heat-treated time and immersion temperature on the corrosion resistance of Mg-4Nd- x Zn alloys were investigated. The results show that except Mg 41 Nd 5 remains in the corrosion product film, there is also the oxides (Nd 2 O 3 and ZnO) and insoluble matter (Mg 2 Cl(OH) 3 ·4H 2 O and Mg(OH) 2 ). Theoretically, the more precipitates, the poorer the corrosion resistance of alloys. However, the Mg-4Nd-3Zn alloy exhibits better corrosion resistance than Mg-4Nd-2Zn alloy, which is attributed to the fact that the oxides formed in the oxidation of precipitates during the microgalvanic corrosion. In addition, the poorer the corrosion resistance of alloys, the more Mg 2 Cl(OH) 3 ·4H 2 O generated on alloys surfaces. • The minor content of oxides is ineffective on corrosion inhibition. • Numerous of Nd 2 O 3 and ZnO embedded in films could prevent Mg alloys from attacking by Cl - . • Mg(OH) 2 will undergo corrosion reaction to generate Mg 2 Cl(OH) 3 ·4H 2 O by consuming H + and Cl - . • The pine-like Mg 2 Cl(OH) 3 ·4H 2 O film is easy to fall off from the alloys surface.