Smart epoxy coating containing inhibitor-loaded cellulose nanocrystals for corrosion protection of steel

The aim of this work is to prepare a smart anti-corrosion coating based on epoxy to effectively protect ST-37 steel alloy. First, Losartan Potassium (LP) as corrosion inhibitor was loaded on cellulose nanocrystals (CNCs). Then, LP-loaded CNCs (CNC@LP) were added to the epoxy coating at an appropriate concentration. It is expected that the losartan potassium will separate from CNCs due to pH changes caused by corrosion and be absorbed in damaged areas, leading to significant improvement in the corrosion protection performance of the epoxy coating. Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), and Thermal Gravimetric Analysis (TGA) were used to characterize the CNC and CNC@LP. Also, the neat and nanocomposite epoxy coatings were characterized by FESEM, AFM (Atomic Force Microscopy), TEM (Transmission Electron Microscopy). In addition, the water contact angle measurement was used to study the wetting properties of the epoxy coatings. Electrochemical Impedance Spectroscopy (EIS) tests showed that the polarization resistance (Rp) of the neat epoxy coating after 168 h immersion in 0.1 M HCl was 0.658 MΩ cm2, which increased to 3.272 MΩ cm2 after adding CNC@LP nanocrystals. This result, which shows a significant improvement in corrosion resistance, is related to the intelligent release of losartan potassium and its absorption at the damaged areas confirmed by UV–Visible Spectroscopy. Also, the results of the EIS tests were checked by taking visual images in the end of the corrosion tests.