Effects of molecular weight, end group of polylactide and coating thickness on corrosion rate and inhomogeneity of iron under biomimetic condition

Iron-based biodegradable stents hold significant promise for percutaneous coronary intervention. Our previous study has revealed that a polylactide (PLA) coating can not only accelerate iron corrosion but also mitigate corrosion inhomogeneity, presenting a metal-polymer composite stent (MPS). Nevertheless, current understanding of how PLA coating parameters regulate iron corrosion remains limited. This article represents the systematic and quantitative in vitro investigation into the effects of coating thickness, molecular weight, and end group of PLA on the corrosion rate and inhomogeneity of an iron substrate under biomimetic condition. By theoretically developing an equation set to quantify random degradation with time-dependent inhomogeneity and experimentally combining immersion corrosion tests with electrochemical analysis, we elucidate the spatiotemporal evolution of iron corrosion under different coating parameters. Our findings provide a crucial foundation for optimizing the degradation behavior of MPS and stimulating for design of other biodegradable materials.