Anti-corrosion behaviour of epoxy composite coatings with silica

The epoxy composite coatings were applied on the mild steel substrates by embedding 1 wt. % mesoporous silica with (E/MSInh) or without (E/MS) inhibitor. Characterisation of the synthesised mesoporous silica loaded with molybdate demonstrated the pH-dependence of molybdate release from E/MSInh. According to the results, by increasing the pH from 1 to 14, a 160 times increase in the molybdate concentration in the solution was observed.

Corrosion inhibiting effect

The corrosion behavior of the composite coatings was assessed by the electrochemical impedance spectroscopy and the electrochemical noise analysis. Charge transfer resistance decreased from 4 × 107 to 3.1 × 104 Ω cm2 and from 2.2 × 106 to 2 × 103 Ω cm2 for E/MSInh and E/MS during the immersion time, respectively. The results revealed the higher corrosion resistance of E/MSInh during 56 days of immersion in 3.5 wt. % NaCl solutions in comparison to E/MS which confirms the proper corrosion inhibiting effect of the released molybdate ions.

The study is published in: Progress in Organic Coatings Volume 126, January 2019, Pages 18-27.