Protective effect of silicone-modified epoxy resin coating on iron-based materials against sulfate-reducing bacteria-induced corrosion

The annual economic loss caused by microbiologically influenced corrosion (MIC) is over 140 billion US dollars worldwide. A sizable proportion (30 %) of MIC is caused by sulfate-reducing bacteria (SRB). Herein, a silicone-modified epoxy resin coating was designed with the aim of reducing the rate of SRB-induced corrosion. The epoxy resin (E-51) was modified with heptamethyltrisiloxane and 3-aminopropyltriethoxysilane (APTES). Compared to the pure epoxy coating (E-51), the modified coating (TAK550/E-51) had a better protective effect against acid- and SRB-induced corrosion owing to its macroscopic and microscopic morphology. Electrochemical impedance spectroscopy revealed that the impedance of TAK550/E-51 coating was 1.5-times higher than that of the E-51 coating, providing it with higher corrosion resistance. In addition, the TAK550/E-51 coating had a lower corrosion current density (icorr = 3.30 × 10−9 A·cm−2) and higher corrosion potential (Ecorr = −0.04 V) than the E-51 coating. The thermal stability of the TAK550/E-51 coating was improved compared to that of the pure epoxy resin coating, with a 9.2 °C higher initial decomposition temperature (T5%), 40.8 °C higher 50 % weight-loss temperature (T50%), and doubled carbon residue rate. The elemental composition and valence state of the coating surface were examined by X-ray photoelectron spectroscopy after immersion in SRB-containing solution for different time periods, which revealed the antibacterial and anticorrosion mechanisms of the TAK550/E-51 coating. The results reported in this paper demonstrate that the silicone-modified epoxy coating has good MIC resistance and can be used as a protective coating for iron-based materials that are susceptible to MIC in industries such as marine engineering and oil exploration.