Corrosion protection of sol–gel coatings doped with an organic corrosion inhibitor: Chloranil

Hybrid sol–gel films have been prepared with diethoxydimethylsilane (DEODMS), methyltriethoxysilane (MTEOS) as a source of hydrolysable silane and tetra-propoxyzirconium (TPOZ) as a source of hydrolysable zirconium. In order to improve corrosion protection, an organic corrosion inhibitor: tetrachloro-p-benzoquinone (chloranil), has been incorporated into the sol–gel matrix. The effect of chloranil, added with various concentrations from 3 to 12 × 10⁻⁴ M, on the sol–gel film morphology and composition has been examined by atomic force microscopy (AFM) and glow discharge optical emission spectroscopy (GDOES), respectively. Addition of high additive concentrations (>9 × 10⁻⁴ M) strongly disorganised the sol–gel network. The anticorrosion properties of the doped sol–gel films have been characterised by electrochemical impedance spectroscopy (EIS) in chloride solution and have been compared to salt spray observations. Chloranil additions (<9 × 10⁻⁴ M) have significantly increased the corrosion protection of the sol–gel layers for a long term.