Design and Performance of a High-Efficiency Inhibitor: Synergistic Effect of Modified Chitosan and Boron Nitride Nanosheets on Steel Protection

Metal corrosion causes significant economic losses and safety hazards, underscoring the urgent need for effective, environmentally friendly corrosion inhibitors. In this study, an organic–inorganic composite inhibitor, chitosan–glucose–BN (CS–GL–BN) was developed to protect Q235 mild steel in a 3.5-wt% NaCl solution. The inhibitor was synthesized by first reacting chitosan (CS) with glucose (GL) via a Schiff base reaction between the amino group of CS and the aldehyde group of GL, followed by the incorporation of hydroxylated boron nitride (OH-BN). Electrochemical measurements demonstrated an inhibition efficiency of 89.8% at 200 ppm after 72 h immersion, which was markedly higher than those of pure CS (64.3%) and the CS–GL intermediate (75.8%). The water contact angle on the steel substrate increased to 91.1°, indicating enhanced hydrophobicity, while the surface roughness was reduced to 0.694 μm (compared with 5.318 μm for bare steel). These combined surface modifications effectively hindered the penetration of corrosive agents. Molecular modeling studies further revealed that the N/O heteroatoms contributed to strong adsorption, thereby significantly blocking the access of corrosive species. This work presents a synergistic strategy in which CS is functionalized with a long-chain molecule (GL) and integrated with BN to form a hybrid corrosion inhibitor that exhibits high efficiency and improved sustainability.