In-situ study of the corrosion process of biodegradable magnesium alloys

The interest in magnesium and its alloys considerably increases in recent years. These materials have a unique complex of properties: light-weight and strength make magnesium alloys promising structural materials for the aircraft industry and space application, and ability to reabsorb in vivo conditions and good biocompatibility allow producing biodegradable surgical implants of magnesium alloys, which can resorb in a human body without detriment to health. The materials for such demanding applications require detailed investigation of their properties, such as corrosion, including the kinetics of corrosion rate and staging of corrosion damage on the surface. To obtain a full view of the corrosion process, in addition to common ex-situ methods such as the corrosion rate evaluating using the weight loss method and the morphology corrosion damage investigation by optical or confocal laser scanning microscopy (CLSM), it is important to use modern in-situ methods. In-situ methods allow obtaining data immediately during the experiment and not after its completion. The authors carried out a comprehensive study of the corrosion process of the commercial ZK60 and AZ31 magnesium alloys in the simulated human-body environment (temperature, corrosion media composition, circulation of corrosion media) using in-situ methods, including hydrogen evolution corrosion rate evaluating and video-observation of a sample surface. The results show that AZ31 alloy is more corrosion-resistant than ZK60 alloy. Moreover, AZ31 alloy is prone to filiform surface corrosion, and ZK60 alloy exhibits severe pitting corrosion. Based on the comparison of the data obtained by in-situ and ex-situ methods, the authors concluded on their main differences and features.