Inhibition Mechanism of a Tea Polyphenols and Zinc Acetate Composite Corrosion Inhibitor for Carbon Steel

Traditional phosphorus-based corrosion inhibitors pose severe environmental risks. To provide a sustainable alternative, an eco-friendly composite inhibitor (TP-AC) combining tea polyphenols (TP) and zinc acetate (AC) was developed to protect carbon steel. Its performance and mechanisms were evaluated via weight loss tests, electrochemical measurements, SEM, and XPS. Results show TP-AC is a highly efficient mixed-type inhibitor, offering superior, longer-lasting protection than AC alone. Its spontaneous, exothermic chemisorption onto the steel surface follows the Langmuir isotherm. Mechanistically, TP and AC exhibit strong synergy: AC-derived Zn(II)–O-containing species, likely including ZnO, contribute to the inorganic component of the protective film, while the phenolic hydroxyl groups of TP interact with surface Fe species to suppress anodic dissolution. Together, these organic and inorganic species form a dense, stable hybrid passivation film, effectively isolating the metal from the corrosive medium. This work provides a theoretical basis for green, high-performance metal protection in industrial circulating cooling water systems.