Fabrication of calcium carbonate coating on magnesium-neodymium alloy for mitigation of corrosion in simulated concrete pore solution

Coating is frequently regarded as one of the most important ways to improve the corrosion behavior of magnesium alloys, and this study proposes a simple strategy for corrosion protection of Mg alloys by chemical solution deposition. A magnesium-neodymium (Mg-Nd) alloy is treated in an aqueous solution prepared with sodium bicarbonate and calcium chloride. After being soaked at 50 °C for 4 h, a layer of uniform calcium carbonate coating with a thickness of about 20 μm has been successfully deposited on the Mg-Nd alloy. Both the electrochemical test and immersion test confirm that this coating significantly improves the corrosion resistance of the Mg-Nd alloy in simulated concrete pore solution containing Cl⁻. The wetting behavior of the coated sample can be further changed by chemical surface modification with perfluorodecyltriethoxysilane (PFDS), which is confirmed by contact angle test, sliding angle test and self-cleaning test. The hydrophobic nature of the modified surface is thought to be responsible for the self-cleaning ability. In summary, it implies that the Mg alloy with a protective calcium carbonate coating has the potential to be used as a type of new civil and building material for lightweight construction.