Designing corrosion-resistant Mg alloys via second-phase control

Abstract

Due to their inherent lightweight property, Mg alloys are considered one of the most attractive structural materials for mobile goods such as personal vehicles and portable devices. However, industrially using Mg-based products in a variety of weight-sensitive components is still rather limited especially due to their poor corrosion resistance. It has been reported that the poor corrosion resistance of Mg-based materials is closely related with the occurrence of active microgalvanic corrosion between the Mg matrix and second-phase particles. Here, we report highly corrosion-resistant Mg alloys whose corrosion resistance is equivalent to that of high-purity Mg, which is expected to be nearly free of microgalvanic corrosion in corrosive conditions. The excellent corrosion resistance appearing in the newly developed Mg alloys is considered attributable to the reduced nobility of cathodic second-phase particles after controlled microalloying with rare-earth elements, resulting in significantly retarded microgalvanic corrosion in 3.5% NaCl solution. Metallurgical factors affecting the electrochemical nobility of cathodic second-phase particles will be discussed.