Optimal cerium microalloying enhances SASS/Q235 weld corrosion and antibacterial performance

Super austenitic stainless steels (SASS) face challenges like galvanic corrosion and antibacterial performance when welded to carbon steel (Q235) in marine environments. This study demonstrates that adding 1.0 wt% cerium (Ce) to SASS refines the heat-affected zone (HAZ) grain structure (from 7 μm to 2 μm), suppresses detrimental σ-phase precipitation, and forms a dense oxide film. Electrochemical analyses confirmed this optimized composition increases charge-transfer resistance (to 2.2 × 10³ Ω cm²) and reduces passivation current density (to 0.12 μA/cm²), significantly enhancing corrosion resistance. Additionally, 1.0 wt% Ce disrupts sulfate-reducing bacteria (SRB) membranes, reducing survival to <1%. However, excess Ce (≥1.5 wt%) forms coarse CeO₂ particles, accelerating corrosion via porous films and micro-galvanic coupling. These findings provide a practical strategy for designing corrosion-resistant, antimicrobial welded joints in marine infrastructure.