High-Efficiency Dual Protection of Photoelectrochemical Cathodic Protection Coating with In2o3/C3n4/Cnt Nanocomposites for 304 Stainless Steel in Marine Environment

Abstract

A photoelectrochemical cathodic protection coating with EP/In2O3/C3N4/CNT composite was designed and its anti-corrosion mechanism was further investigated. It was found that the introduction of In2O3/C3N4 not only densified the microporous structure but also enhanced the hydrophobicity, tensile strength and UV aging resistance of epoxy resin (EP) coatings. The corrosion current (Icorr) of 304 SS/EP/In2O3/C3N4/CNT reduced by 95.8% and 67.8% of that of 304SS and 304 SS/EP in dark, respectively, due to the enhanced physical shielding effects of In2O3/C3N4/CNT nanoparticles. Under illumination, the OCP values of EP/In2O3/C3N4 and EP/In2O3/C3N4/CNT composite coatings were rapidly shifted negatively to -170 mV and -274 mV, respectively, which were both lower than the self-corrosion potential of 304 SS. That was owing to the photocathodic protection of In2O3/C3N4/CNT, where the photogenerated electrons produced by In2O3/C3N4 nanocomposites transferred to surface of 304 SS through the electronic transmission network of CNT under illumination. The introduction of optoelectronic nanoparticles into coatings is believed to be an effective strategy for providing dual protection for metals, which not only improved the physical shielding effects of the coating but also enhanced the photocathodic protection performance at the dark state.

Keywords: Marine, Corrosion, Steel, Photoelectrochemical Cathodic Protection, Coating