Effective anticorrosion coatings prepared from sulfonated electroactive polyurea

Abstract

In the present study, the sulfonated electroactive polyurea (S-EPU) was first prepared and characterized, applied as an anticorrosion coating. The electroactive oligomer sulfonated amine-capped aniline trimer (S-ACAT) was synthesized by oxidative coupling reaction, followed by characterization using Fourier-transform infrared (FTIR) and mass spectroscopy (MS). For the preparation of sulfonated electroactive polyurea (S-EPU), isophorone diisocyanate (IPDI) was reacted with poly(tetramethylene ether) glycol (PTMEG) in the presence of a specific amount of diamine S-ACAT. The success of the S-EPU was confirmed through FTIR and GPC. After that the redox capability of as-prepared S-EPU was confirmed by CV studies. Chemical oxidization of S-EPU, carried out through the introduction of trace amount of ammonium persulfate, was monitored by UV-VIS spectroscopy. The electrochemical corrosion of the electroactive polymer-coated cold-rolled steel (CRS) electrode, in neutral, acidic and alkaline conditions, were measured and compared. As compared to non-electroactive polyurea (N-EPU), results showed enhanced corrosion protection of the S-EPU coating and electroactive polyurea (EPU) coating, owing to their redox capability that induces the formation of densely passive metal oxide layer (e.g., Fe2O3 and Fe3O4). The densely metal oxide layers induced by S-EPU/EPU coatings were further confirmed by Raman spectroscopy, SEM and ESCA. Moreover, the S-EPU coating exhibited better anticorrosion performance than that of EPU coating which could be attributed to the higher electro-catalytic property of S-EPU coating upon CRS electrode, causing the formation of more densely metal oxide layers to shelter the underlying metal substrate.