Enhanced corrosion resistance of layered double hydroxides/steam coating composite coating prepared by the hydrothermal method on LA43M magnesium–lithium alloy substrates

Abstract

An excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X‐ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long‐term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest Icorr (1.767 × 10−8 A/cm2), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm−2·h−1) and weight lost rate (0.00266 mg·cm−2·h−1) were the lowest compared with other samples.