Identification and development of a new local corrosion mechanism in a Laser Engineered Net Shaped (LENS) biomedical Co-Cr-Mo alloy in Hank’s solution

In this work, the microstructure and the corrosion behavior of a biomedical grade Co-Cr-Mo (CCM) alloy manufactured by laser engineered net shaping (LENS) was characterized. Electron microprobe maps identified the micro-segregation of Cr and Mo to the cell boundaries in the microstructure of the LENS alloys. Cyclic polarization in Hank’s solution and study of the corroded surface under scanning electron microscopy (SEM) revealed the development of micro-galvanic cells and new crack-like features which served as active sites of localized dissolution of the alloy. Based on this evidence, a new corrosion mechanism that constituted of selective dissolution of Cr/Mo-depleted regions and development of crack-like features at junctions between the various cell types was proposed for LENS CCM alloys.