Enhancing corrosion resistance of additively manufactured magnesium alloys via in-situ reaction-driven dual mechanisms

Mg and its alloys hold significant promise as biomedical materials, but their orthopedic applications are limited by inadequate corrosion resistance. This study proposed a dual-effect corrosion inhibition strategy mediated by in-situ reaction. Specifically, CaO nanoparticles were incorporated into ZK60 via laser powder bed fusion to function as reactive peritectic, reacting with the Mg melt to form MgO and Mg 2 Ca phases. Upon degradation initiation, MgO undergoes rapid hydrolysis to generate a protective Mg(OH) 2 layer that provides immediate barrier protection. Concurrently, the Mg 2 Ca phases act as sacrificial anode within galvanic couples relative to the α-matrix grains. These phases preferentially degrade to deliver cathodic protection to Mg grains while producing Ca-enriched products that densify the corrosion layer, thereby retarding overall degradation. Volta potential measurements confirmed the sacrificial anode function of Mg 2 Ca, exhibiting approximately 130 mV more negative potential than the α-Mg matrix. Electrochemical testing demonstrated that CaO incorporation significantly enhanced the corrosion resistance of ZK60 alloy throughout both initial and prolonged exposure periods. Mott-Schottky analysis revealed that the ZK60-CaO displayed characteristic n-type semiconductor behavior with reduced carrier concentration (approximately 1.29 × 10 22 cm −3 ) than ZK60 alloy, indicative of a denser, more protective corrosion product film versus ZK60. After immersion for 24 h, the corrosion rate of ZK60-CaO alloy was decreased from 1.54 mm/y to 0.35 mm/y, confirming that the CaO-formed passive layer effectively retarded the alloy degradation. This synergistic dual-effect strategy offers a promising approach to improve corrosion resistance and extend the functional lifespan of Mg-based implants. • A novel dual-effect corrosion inhibition strategy is proposed for Mg alloy via in-situ reaction. • The strategy combines rapid Mg(OH) 2 formation from hydrolysed MgO and sacrificial anode of Mg 2 Ca phases. • Sacrificial Mg 2 Ca degradation enriches Ca in the corrosion layer, densifying it and further retarding degradation. • The ZK61-CaO exhibits superior corrosion resistance due to a denser and more protective n-type semiconductor film.