Catalytic Cu-ion regulation in laser-directed energy deposited stainless steel coatings for sustainable surface biofouling mitigation

Abstract In this study, the laser-directed energy deposition technology was adopted and combined with pre-alloyed Cu-bearing stainless steel (SS) powders to successfully fabricate advanced metal-based antifouling coatings suitable for marine engineering. The optimized 304L-5Cu SS and 304L-10Cu SS coatings exhibited dense microstructures with uniform Cu distribution, significantly reducing bacterial activity within 24 h and inhibiting biofilm adhesion by suppressing polysaccharide and protein secretion. In a novel dynamic antifouling evaluation system, the biofouling coverage on the Cu-bearing SS coatings decreased to 2.5% after 7 days, with fouling inhibition rates increasing from 58.3% to 82.1% as Cu content rose. In comparison to commercial copolymer coatings, the Cu-bearing SS coatings demonstrated reduced and more controlled Cu ion release rates, effectively minimizing environmental risks to marine ecosystems. The enhanced antifouling performance was attributed to the catalytic generation of reactive oxygen species induced by Cu ions, leading to cellular damage. Additionally, the 304L-10Cu SS coating showed superior uniform corrosion resistance, although its pitting potential decreased by approximately 41.1% compared to the 304L-5Cu SS coating due to CuO dissolution at high potentials. These findings highlight the potential of LDED-based surface modification for designing sustainable, high-performance antifouling coatings, offering a resource-efficient and environmentally-friendly solution for marine equipment applications.