Investigation of loaded halloysite nanotubes with novel inhibitor as a smart anticorrosion epoxy coating

Abstract

In this work, a smart epoxy coating was applied based on encapsulation of 3,4′-dihydro-3-[2′-mercaptothiazolidine]indol-2-one (DMI) inhibitors to halloysite nanotubes (HNTs) as nanocontainer for corrosion inhibition of API 5L Grade B carbon steel in 3.5% NaCl solution. Transmission Electron Microscope (TEM) and Brunauer–Emmett–Teller (BET) analysis methods were used to confirm the encapsulation of HNTs with DMI. Layer-by-Layer (LbL) deposition of polyelectrolytes (Branched Polyethylenimine (BPEI) and Poly (ethylene-co-acrylic acid) (PEAA)) on HNTs was validated by zeta potential test. Releasing rate of the inhibitors in various pH conditions were characterized by UV-visible spectroscopy. Electrochemical impedance spectroscopy (EIS), Tafel polarization and salt spray tests were used to evaluate the active anticorrosion ability of 1, 2.5 and 5 wt% of HNTs and DMI-loaded HNTs epoxy coatings. In comparison with blank epoxy coating, higher value of charge transfer resistance, lower value of double layer capacitance (constant phase element) in EIS results and decreasing the density of corrosion current in Tafel curves showed anticorrosive performance of the smart coatings. 2.5% DMI-loaded HNTs coating showed significant effect on corrosion protection of carbon steel samples and was introduced as optimum weight percentage.