An integrated epoxy rust conversion coating: Its anticorrosion properties and rust conversion mechanism

Highlights:• A new integrated epoxy rust conversion coating was successfully prepared.• It combined the primer and topcoat of traditional coatings into one.• It simplified construction process and improved construction efficiency.• Rust conversion agent can form complex of Fe–O–C structure with iron ion. -- Abstract: A new rust conversion agent based on gallic acid was developed. On this basis, an integrated epoxy rust conversion coating that combined the primer and topcoat of traditional coatings into one was prepared. Compared with the traditional coatings, the integrated epoxy rust conversion coating in this study appeared significant performances: (1) It simplified the construction process, and strengthened the adhesion between rust conversion coating and rust/substrate; (2) In corrosion simulation environments, i.e., the natural environment, water immersion environment and weather-resistant accelerated aging environment, the surface of integrated epoxy rust conversion coating was smooth, and contained fewer holes. Meanwhile, the contact between the coating and substrate or rust was relatively close. Additionally, the corrosion potential and corrosion current density respectively were −0.465 v/7.247 × 10⁻⁷ A/cm², -0.736 v/5.958 × 10⁻⁵ A/cm², and -0.574 v/2.305 × 10⁻⁶ A/cm². (3) The degree of rust conversion was delectable, and rust conversion mechanism showed that the components of original rust were transformed into stable phases, i.e., the phenolic hydroxyls contained in rust conversion agent can form a series of stable complexes with Fe–O–C structure by chelating with iron ion, thus inhibiting further rust expansion.