Corrosion protection of carbon steel by an epoxy resin containing organically modified clay

This study focusses on the use of montmorillonite clay (MMT) treated with an organic compound (aminotrimethylphosphonic acid (ATMP)) and dispersed in an epoxy resin to improve corrosion protection of carbon steel. X-ray diffraction was performed to verify that the individual silicate layers were separated and dispersed in the epoxy resin. Corrosion resistance of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and local electrochemical impedance spectroscopy (LEIS). Three systems were tested: the epoxy clear-coat, the epoxy resin containing 2 wt.% clay and the epoxy resin containing 2 wt.% clay modified by ATMP (ATMP-modified clay). From conventional EIS, it was shown that the incorporation of clay or ATMP-modified clay in the epoxy matrix significantly improved the barrier properties of the coating. The corrosion resistance of the carbon steel coated by the epoxy resin containing ATMP-modified clay was higher than that obtained for the system containing non-treated clay. Local electrochemical measurements performed on scratched samples revealed the inhibitive role of ATMP at the carbon steel/coating interface.