Applying metals without passivation ability in corrosive environments presents a significant challenge. Medium manganese steel (MMS), a widely used wear-resistant metal, had been investigated for its tribocorrosion behavior following critical annealing at different temperatures, with potential applications in seawater. Notably, the new MMS alloy, designated as 5MnAl, demonstrates superior corrosive wear resistance compared to 316L stainless steel (SS) in a 3.5% NaCl solution, with an average wear rate reduction ranging from 69.3% to 93.9% and lower friction coefficients under 10–60 N load. Specifically, the corrosive wear rate of 316L SS is more than 16 times higher than that of 750 °C annealed 5MnAl under an applied load of 60 N. Additionally, corrosion-induced wear volume loss (Vcw) typically accounts for more than half of the total volume loss. The corrosive wear rate of 5MnAl can be significantly reduced by applying a cathodic protection potential of -1.2 V. Consequently, due to its outstanding resistance to mechanical wear, metals without passivation ability may offer superior prospects for use in friction components in seawater environments compared to 316L SS.