The regulation of organic molecules to the morphology and corrosion protection ability of CaCO3 coating on biomedical MgZnCa alloy

Abstract

A controllable corrosion rate is an ideal condition for magnesium (Mg) alloy as biodegradable metallic materials. Calcium carbonate (CaCO3) coating has been proven to possess a robust anti-corrosion property for Mg alloy. To further regulate the morphology and corrosion protection ability of the CaCO3 coating, in current study, different organic molecules, including amino acids (Tyr and Glu), amine (DOPA), proteins (COL and BSA) and peptide (CPP), were added into the coating formation electrolyte, affecting the morphology, polymorph composition, and the crystal size distribution of precipitated CaCO3. The results revealed that Tyr exhibited little effect on the polymorph composition of the CaCO3-based coating, while Glu, DOPA, COL and BSA generally promoted the formation of vaterite but inhibited the formation of rod-like aragonite precipitates and calcite in the coatings. In contrast, CPP suppressed the precipitation of CaCO3 crystals because of its high affinity to Ca2+ ions. The addition of those organics reduced the size of calcite crystals. Consequently, the organic molecules mediated CaCO3-based coatings showed better compactness and homogeneity, which maintained the strong adhesion strength of the coatings to the substrate and further enhanced the corrosion protection abilities of the coating for the substrate. The results of the study pave the way for the development of CaCO3-based coatings with advanced properties for Mg alloys as biomedical materials.