A layer-by-layer assembled coating for improved stress corrosion cracking on biomedical magnesium alloy in cell culture medium

Magnesium (Mg) alloys have shown great potential for biomedical implant materials due to their biodegradability and suitable mechanical strength. Recent works have shown that biomedical Mg alloys suffered from accelerated degradation rates when exposed to a stressed condition in biological media. Therefore, it is necessary to endow Mg alloys with enhanced stress corrosion cracking resistance. In this study, phytic acid (PA), branched polyethylenimine (bPEI) and graphene oxide (GO) were introduced onto Mg1Zn alloy via layer-by-layer (LbL) assembly technique. The characteristics of the multilayer films were investigated by SEM, FTIR and XPS. Biodegradability Corrosion resistance of the samples was measured by electrochemical and immersion tests. The stress corrosion cracking (SCC) behaviour of the LbL coated Mg alloys was performed using slow strain rate tensile (SSRT) tests. The results showed that the multilayer coating with smooth and uniform morphologies could enhance the corrosion resistance of Mg alloys due to the physical barrier. The LbL coating exhibited a remarkable ability to improve the SCC resistance of Mg1Zn alloy in Dulbecco's modified eagle medium. •A layer-by-layer (LbL) assembled coating with bPEI, GO and PA was prepared.•The physical barrier of LbL coating is contributed to excellent corrosion resistance.•The LbL coating significantly improved stress corrosion cracking (SCC) of Mg alloy.•PA conversion film enhanced anti-corrosion while was detrimental to SCC.