Environmental Risk Assessment and Anti‐Corrosion Efficacy of Safe‐by‐Design Nitrite‐Based Nanomaterials for Maritime Applications

Metallic corrosion is an unsolved economic and environmental problem, mitigated with coatings often containing toxic corrosion inhibitors. This study aims to extensively assess two eco‐friendly and efficient anti‐corrosion nanomaterials for maritime applications, specifically layered double hydroxides containing nitrite (Mg‐Al LDH‐NO 2 and Zn‐Al LDH‐NO 2 ) in terms of anti‐corrosion performance, ecotoxicity, and environmental behavior and risk, along with a novel polyurethane coating. In aqueous dispersions, both LDHs behave as stimuli‐responsive materials: unstable, tendency to rapidly aggregate and sink and release chemicals through anionic exchange and partial dissolution. Both nanomaterials presented negligible toxicity to most species, except microalgae Isochrysis galbana . Zn‐Al LDH‐NO 2 also caused effects on the gastropod Phorcus lineatus and the echinoderm Paracentrotus lividus , being the most hazardous compound. Considering the environmental concentration of NO 2 − , reported in the literature for well‐oxygenated open ocean waters, and the statistically predicted no effect concentrations, tested chemicals potentially represent no environmental risk. The novel coating containing Zn‐Al LDH‐NO 2 showed improved corrosion protection of carbon steel when benchmarked with state‐of‐the‐art coatings. Leachates from these coatings also caused no/low ecotoxicological effects, attributed to the low release of chemicals over four weeks of immersion. These breakthroughs demonstrate that these novel ENMs are environmentally promising anti‐corrosion nanoadditives for maritime coatings.