Highly soluble glyoxal-modified guanine as a green corrosion inhibitor for Q235 carbon steel in seawater environments

Q235 carbon steel is widely used in seawater cooling systems but suffers severe corrosion in high-salinity environments. Conventional inhibitors are limited by poor water solubility and environmental risks. Here, we synthesized glyoxal-modified guanine (GGO) by introducing hydrophilic – OH groups and coordination-active (C = N/C – N) sites, increasing aqueous solubility from < 1 mg/L (guanine) to 3.289 g/L. Electrochemical and weight loss tests showed that GGO achieved a corrosion inhibition efficiency of 96.15% at 200 ppm in 3.5 wt.% NaCl, greatly surpassing unmodified guanine. SEM, contact angle, and 3D profilometry revealed that GGO formed a compact, hydrophobic protective film, significantly reducing corrosion pits and surface roughness. Adsorption isotherms and thermodynamic analysis indicated that GGO adsorption involves both chemisorption and physisorption, with a more negative Gibbs free energy than guanine. Quantum chemical calculations and molecular dynamics simulations demonstrated that polar functional groups promote strong adsorption and coordination with the steel surface, blocking chloride attack and stabilizing the inhibitor layer. XPS confirmed Fe – N coordination bonds and organic species in the protective film. This study provides a high-efficiency, eco-friendly corrosion inhibition strategy for Q235 carbon steel in saline environments and guides the rational design of green inhibitors for industrial applications.