One-pot synthesis of NiAl–CO3 LDH anti-corrosion coatings from CO2-saturated precursors

Abstract

Anti-corrosive coatings based on layered double hydroxides (LDHs) have been considered as promising alternatives to conventional chromate-containing conversion coatings. Among various LDHs, carbonate-intercalated LDH coatings with a c-axis preferred orientation should be the optimum structure for protecting metals against corrosion. Herein we successfully prepared NiAl–CO₃ LDH coatings on aluminium plates in one step. Particularly it was found that CO₂ dissolved in the precursor solution exerted great influence on the microstructure and anti-corrosion capacity of prepared LDH coatings. Trace amounts of CO₂ in the precursor solution led to the formation of ab-oriented 7 μm-thick LDH coatings, while preferentially c-oriented LDH coatings with an average thickness of 12 μm were formed from CO₂-saturated precursor solutions. A DC polarization test demonstrated that preferentially c-oriented LDH coatings exhibited much higher anti-corrosion performance than ab-oriented LDH coatings possibly due to the decreased density of mesoscopic defects. Simultaneously, CO₂, the green gas, was also positively utilized.