Corrosion behavior and protection mechanism of carbon steel coated with ethylene chlorotrifluoroethylene (ECTFE)

Ethylene chlorotrifluoroethylene (ECTFE) coating was applied to the surface of carbon steel through electrostatic spraying and low-temperature heat treatment. The morphology and structure of the coating were analyzed using various characterization techniques. The electrochemical data of the coated steel soaked in 3.5% (mass fraction) NaCl solution for 90 d at different periods were also examined. The findings indicate that the outer surface of the coating remains structurally stable before and after soaking. F can diffuse into the steel substrate, facilitating the bonding between the coating and the steel substrate, but the free F also induces a weakening effect on the crystalline structure. Due to the thickness of the coating edge and the susceptibility to infiltration of the corrosive medium, under-film micro-zone corrosion occurs at a slow rate. After soaking for 90 d, the impedance modulus measures approximately 10⁴ Ω·cm², and the open circuit potential (OCP) is −0.61 V. The self-corrosion current density is 1.13×10⁻⁶ A/cm², resulting in a calculated coating protection rate of 99.29%. In summary, despite edge corrosion occurring, the ECTFE coating provides excellent corrosion protection.