Lanthanide salts in sustainable corrosion protection: Chemistry, progress, mechanism, challenges and opportunities

Many sectors, including the oil and gas sector, face significant challenges from electrochemical degradation, or the corrosion of metallic materials, because of material deterioration, loss of mechanical strength, safety hazards, environmental effects, and significant financial losses. Inorganic salts, particularly cerium (Ce), samarium (Sm), lanthanum (La), and praseodymium (Pr), show promise as sustainable substitutes for conventional harmful corrosion inhibitors such as chromates, molybdates, nitrites, etc., for modern applications. This article provides a thorough overview of chemistry, mechanism of action, advancements, difficulties, and prospects of employing inorganic salts for next-generation sustainable corrosion protection. These eco-friendly salts provide excellent corrosion protection by inhibiting the anodic and cathodic reactions by forming surface oxides and hydroxides and blocking the diffusion of corrosive species to the metal surface. Ce shows 98.9 % corrosion efficacy against mild steel in 3.5 % NaCl. The effectiveness of the other inorganic salts is similarly around 90 %. The efficiencies of samarium salts for steel, magnesium alloys, and API 5 L X70 steel were 92.0 %, 98.42 %, and 87.9 %, respectively. Additionally, it was found that conversion coatings based on Sm(III) could minimize cathodic delamination by as much as 78 %. Among the different inorganic salts, cerium salts are most frequently utilized for aqueous phase corrosion protection of Al, Fe, and Mg alloys. Samarium-based salts are mostly used in anticorrosive coating applications. The literature study shows that recently, the presence of inorganic salts in smart coatings, graphene, polymer-based composites, and sol-gel matrices results in the formation of novel multifunctional materials for enhanced anticorrosive activities. These materials have been widely reported for their self-healing properties. The literature study suggests that the corrosion inhibition potential of inorganic salts remains unexplored despite their association with many benefits and opportunities as low toxicity, compatibility, long-term stability, self-healing nature, ability to protect corrosion in solution and coating phases, etc. The promise of lanthanide salts in green corrosion inhibitors is also examined, emphasizing the possibilities for sophisticated characterization methods, AI prediction, and computational design. • This article provides a thorough overview of the chemistry, mechanism of action, advancements, difficulties, and prospects of employing inorganic salts for sustainable corrosion protection. • These eco-friendly salts provide excellent corrosion protection by inhibiting the anodic and cathodic reaction by forming the surface oxides and hydroxides and blocking the diffusion of corrosive species to the metal surface. • Ce shows 98.9 % corrosion efficacy against mild steel in 3.5% NaCl. The efficiencies of samarium salts for steel, magnesium alloys, and API 5 L X70 steel were 92.0 %, 98.42 %, and 87.9 %, respectively. • Additionally, it was found that conversion coatings based on Sm(III) could minimize cathodic delamination by as much as 78 %. Among the different inorganic salts, cerium salts are most frequently utilized for aqueous phase corrosion protection of Al, Fe and Mg alloys. • The present article underscores the inhibition potential of inorganic salts as next-generation sustainable corrosion protection.