Preparation of corrosion resistant film on Mg-6Al-1Zn-2Ca alloy by steam coating

Corrosion resistant films were prepared on flame-resistant Mg-6Al-1Zn-2Ca (in mass%) alloy by steam coating using ultra pure water as steam source. The prepared films were characterized using SEM, XRD, and FT-IR. Corrosion resistance of the film was estimated by polarization curve measurement in 5 mass% NaCl aqueous solution. All XRD patterns of the films coated Mg-6Al-1Zn-2Ca alloy revealed that all films were composed of crystalline Mg(OH)2 and Mg-Al layered double hydroxide (LDH). FT-IR spectra showed that the Mg-Al LDH had carbonate- and nitrate-ions in the interlayer. Potentiodynamic polarization curves of the film prepared at 433 K for 6 h indicated that the corrosion current density decreased by more than four orders of magnitude as compared to that of the uncoated Mg-6Al-1Zn-2Ca alloy.