This work investigates the effect of Mg and Ca precipitates on the electrochemical performance of Fe-Mn-Nibased anodes produced through powder metallurgy in simulated and real alkaline seawater. The electrodes that exhibited the best performance in simulated seawater were those containing 60 %Fe-40 %Ni and 15 %Fe-15 %Mn-70 %Fe, both with an overpotential for the oxygen evolution reaction of 370 mV at 10 mA/cm2 and Tafel slopes of 45 and 53 mV/dec, respectively. However, when real alkaline seawater was used as electrolyte, the electrocatalytic ability of these electrodes decreased; the presence of Ca2+ was identified as a significant factor promoting pitting corrosion. The study concludes that a comprehensive investigation into the individual effect of seawater ions on electrode performance is necessary.