Comparative Study of Corrosion Inhibition Properties of Q345 Steel by Chitosan MOF and Chitosan Schiff Base

This study synthesized two eco-friendly inhibitors-a chitosan-copper metal-organic framework (CS@Cu MOF) and chitosan-Schiff base-Cu complex (Schiff-CS@Cu)-for Q345 steel protection in 3.5% NaCl/1M HCl. Electrochemical and weight loss analyses demonstrated exceptional corrosion inhibition: untreated specimens showed a 25.889 g/(m²·h) corrosion rate, while 100 mg/L of CS@Cu MOF and Schiff-CS@Cu reduced rates to 2.50 g/(m²·h) (90.34% efficiency) and 1.67 g/(m²·h) (93.56%), respectively. Schiff-CS@Cu's superiority stemmed from its pyridine-Cu²⁺ chelation forming a dense coordination barrier that impeded Cl^-/H⁺ penetration, whereas CS@Cu MOF relied on physical adsorption and micro-galvanic interactions. Surface characterization revealed that Schiff-CS@Cu suppressed pitting nucleation through chemical coordination, contrasting with CS@Cu MOF's porous film delaying uniform corrosion. Both inhibitors achieved optimal performance at 100 mg/L concentration. This work establishes a molecular design strategy for green inhibitors, combining metal-organic coordination chemistry with biopolymer modification, offering practical solutions for marine infrastructure and acid-processing equipment protection.