Bilayer Polymer Coating for Corrosion Protection of Iron Comprised of a Conductive Polymer Polyaniline and a Polymer with Triazine Rings

Abstract

A poly(2-N-phenylamino-4,6-dimercapto-S-triazine) (PPDT) layer was first prepared on the iron surface electrochemically. The PPDT layer strongly adsorbed on the surface because of the polar triazine rings of the PPDT molecules. The fact that no electrochemical response of the PPDT layer covered electrode to dissolved Fe(CN)₆³⁻ exhibited that the PPDT layer is an insulator layer with less permeability to dissolved species, acting as a diffusion barrier against agents causing corrosion such as H₂O and O₂. A conductive polymer polyaniline (PANI) layer could be electrodeposited on the PPDT layer using the PPDT layer covered electrode. The obtained PANI/PPDT bilayer coating greatly lowered the anodic current peak ascribed to the anodic dissolution of iron and the corrosion current. The high anti-corrosion ability was due to a hybrid effect of the PANI layer as an in-situ oxidant and the PPDT layer as a diffusion barrier.