Investigation of the corrosion for Mg–xGd–3Y–0.4Zr (x = 6, 8, 10, 12 wt%) alloys in a peak-aged condition

The corrosion behaviour of Mg–6Gd–3Y–0.4Zr (GW63K), Mg–8Gd–3Y–0.4Zr (GW83K), Mg–10Gd–3Y–0.4Zr (GW103K) and Mg–12Gd–3Y–0.4Zr (GW123K) were investigated in peak-aged condition using immersion and salt spraying tests and electrochemical measurements in 5% NaCl solution. The corrosion resistances of Mg–xGd–3Y–0.4Zr alloys were found to decrease with the increase of Gd content from 6% to 10% and then increase from 10% to 12%. The corrosion products of Mg–xGd–3Y–0.4Zr alloys were discovered to be composed of voluminous tiny erect flakes by FE-SEM, and the compactness of the corrosion films decreases with the increase of Gd content. The results of AES revealed that the corrosion film is enriched with Gd and Y. The potentiodynamic polarization curves showed that the overpotentials of cathodic hydrogen evolution on GW63K and GW83K are much higher than on GW103K and GW123K. The results of EIS are in good agreement with the morphologies of the corrosion products and the corrosion rates of the corrosion tests.