Mitigating chloride-induced corrosion of metallic bipolar plates in seawater electrolysis systems

Seawater electrolysis is emerging as a promising pathway for sustainable hydrogen production. However, the highly corrosive chloride ions in seawater attack metallic bipolar plate (BPP), which is a key barrier to their practical application. This study compared the corrosion behavior of bare and Ni-coated 316L stainless steel and Q235 carbon steel in alkaline chloride media. Test results showed that Cl - severely degraded passivation films and accelerated corrosion. The nickel (Ni) coating formed by electroplating has effectively mitigated the corrosion issue by forming a protective Ni(OH) 2 /NiO layer, and has improved the conductivity of the BPP. Notably, Ni-coated BPP exhibited excellent electrochemical stability, highlighting their potential as an efficient modification strategy for alkaline seawater electrolysis. The electrochemical stability followed this order: Ni-coated 316L stainless steel > Ni-coated Q235 steel > bare 316L stainless steel > bare Q235 steel. The critical chloride concentration thresholds were determined to be 0.05 M for bare 316L, 0.01 M for bare Q235, and 0.1 M for both Ni-coated materials.