Effect of solution pH on stress corrosion cracking behavior of modified AZ80 magnesium alloy in simulated body fluid

Abstract Magnesium (Mg) and its alloys are widely used as biodegradable materials in orthopedic applications. However, the poor corrosion resistance of Mg alloys in physiological environments largely limits their application in medical implants. In this study, the surface of AZ80 Mg alloy were modified by two treatment methods, micro-arc oxidation (MAO) and the composition of laser shock penning/micro-arc oxidation technology (LSP/MAO). Slow strain rate tensile (SSRT) testing was performed on untreated (BM) and treated (MAO and LSP/MAO) specimens in simulated body fluid (SBF) with various pH values (4, 7.4, and 9) at a strain rate of 5.3 × 10−7 s−1. The scanning electron microscopy (SEM) was used to observe the fracture morphology of corroded specimen. The energy-dispersive X-ray spectroscopy (EDS) was used to analyses elements on corroded surface. The corrosion resistance of different specimens was investigated by electrochemical testing. The results indicated that the MAO specimen itself had the best stress corrosion cracking (SCC) resistance in pH 7.4 SBF, and the worst in pH 4 SBF. The LSP/MAO specimen possessed superior SCC resistance to MAO specimen in SBF with various pH values. The LSP/MAO composite coating can effectively improve the corrosion resistance and mechanical properties of AZ80 Mg alloy, which helps to extend the service life of Mg alloy implants and promote the development of Mg alloys in medical and industrial fields. The SCC mechanisms of three specimens were evaluated in SBF with various pH values.