The corrosion behaviour of different planes of a selective laser-melted (SLM) equimolar CrCoNi mediumentropy alloy (MEA) was investigated and compared with its counterpart cast alloy in a 3.5 wt% NaCl solution. The microstructures of the SLM products were characterised, and electrochemical corrosion measurements, corrosion surface morphology observations, and X-ray photoelectron spectroscopy analyses were performed. Compared with the cast MEA, the SLM MEA has an inferior corrosion resistance for its more metallurgical defects and smaller grain size. In the SLM MEA samples, The XY-plane of the ...