Effects of PHB and PLA coatings on the corrosion behavior of ultrathin Mg sheets in artificial blood plasma containing BSA

Biodegradable polymer coatings are commonly used as protective barriers on magnesium (Mg) and its alloys. The properties of polymers, such as crystallinity and degradation properties, have a crucial impact on their corrosion resistance. In this work, polyhydroxybutyrate (PHB) coatings are deposited on Mg sheets with a thickness similar to that of cardiovascular stents to assess the degradation behavior, and poly-lactic acid (PLA)-coated Mg is also investigated to compare the structure–property-performance relationship. The hydrogen evolution volume (HEV) of the PHB-coated sample decreases by 30% after immersion in artificial blood plasma (AP) for 7 days, whereas the PLA-coated sample shows an increase of 154%. The PHB coating also shows excellent durability at a constant voltage, compared to severe rupture of the PLA coating. The degradation behavior of the coated-Mg samples is evaluated in AP solution containing different concentrations of the bovine serum albumin (BSA). Corrosion is inhibited as the protein concentration increases. The degradation rates of the Mg, PLA-coated Mg, and PHB-coated Mg decrease by 65%, 88%, and 75% for 5 g L⁻¹ BSA, respectively. Our results reveal that higher crystallinity and less acidic degradation products give rise to better durability, while the acid self-catalytic effect leads to the failure of PLA. The protein-polymer interactions are determined and the empirical relationship of HEV is established.

Graphical Abstract