Development of the CaCO3-coated passive film on Mg alloy densified by glucose/sodium gluconate via the assistance of ultrasound with a regrowth feature in Portland cement

Abstract

To address the limitations of non-dense chemical conversion coatings on Mg alloys, glucose and sodium gluconate were employed to facilitate the creation of dual-layered CaCO3 coated MgO passive layers via ultrasound-assisted chemical conversion. Results indicate that the addition of an appropriate quantity of glucose enhances the corrosion resistance of CaCO3/MgO coatings, whereas excessive glucose compromises coating density. Furthermore, higher concentrations of sodium gluconate contribute to improving coating density. Significantly, the immersion in simulated concrete pore solutions with 0.6 M NaCl reveals a re-growth phenomenon instead of corrosion. This observation stems from the increased CaCO3 production, including calcite and aragonite during the immersion process.