Abstract The corrosion and passivation behavior of the as-cast CoCrFeNiMo x ( = 0, 0.2, 0.4, 0.6, 0.8, 1.0) high entropy alloys (HEAs) are investigated. With addition Mo, increasing Mo Cr riched σ phase precipitates from primary FCC phase. resistance HEAs strongly depends on structure passive film. Generally, promotes selective dissolution enrichment 2 O 3 in film, former deteriorates while lat...