Film Formation Behavior and Corrosion Protection Mechanism of Silane‐Enhanced PAA/Zn Composite Coating on Carbon Steel Surface

ABSTRACT This study aims to replace traditional chromium‐containing conversion coatings and overcome the drawbacks of polyacrylic acid (PAA) films, including slow formation, high hydrophilicity, and limited stability. A synergistic strategy using epoxy‐functional silane γ‐(2,3‐epoxypropoxy)propyltrimethoxysilane (KH‐560) and zinc ions constructs a ternary PAA/KH‐560/Zn 2+ composite coating on carbon steel. Silane concentration and formation time were evaluated via electrochemical testing, contact angle, SEM, XPS, and FTIR. Optimal performance is achieved at 0.6 vol% KH‐560 with a 10 min formation time. Under these conditions, the low‐frequency impedance modulus reaches 2.25 × 10 4 Ω·cm 2 , the charge‐transfer resistance is increased by more than one order of magnitude relative to bare steel, and a protection efficiency of 95.7% is achieved, and water contact angle is 95°, indicating hydrophobicity. Protection arises from a ternary synergistic mechanism of “coordination–crosslinking–anchoring,” rapidly forming a dense hydrophobic layer. An electrophoretic paint topcoat two‐layer system validates that the optimized pretreatment layer enhances anti‐corrosion performance under industrial‐relevant conditions. This offers new insights for advancing rapid and eco‐friendly metal surface pretreatment.