Preparation and mechanisms of a modified graphene oxide anticorrosive coating doped with thermochromic material indicating metal equipment thermal malfunction

Metal equipment is susceptible to corrosion and aging under high temperature condition. It is low-cost and effective thermal malfunction detection method by coating temperature-indicating paint on the metal surface. In this study, thermochromic material (TCM) was synthesized by liquid-phase synthesis method in which [CuCl 4 2− ] was used to react with Na 2 EDTA. A temperature-indicating anti-corrosive coating (TIAC) was prepared by dispersing TCM and modified graphene oxide (MGO) into the silicone resin. The microstructure, crystal plane, functional groups, and bonding changes of TCM before and after discoloration were analyzed using FE-SEM, XRD, FTIR, and XPS. Corrosion resistance of TIAC were detected using OCP, Tafel, and EIS experiments. The mechanism of color changes in TCM were studied using density functional theory (DFT) calculation. The results showed that TCM produced a reversible color change from green to yellow when the temperature increased from 80 °C to 300 °C. When the temperature exceeds 300 °C, the TCM had irreversible color change. After heating and discoloration, the C-N bond was broken and the content of COO-Cu increased. A reticular structure appeared on the surface of TCM and the crystal plane spacing reduced. DFT calculation proved that TCM had a high formation energy (E F ) below 300 °C, its structure was unstable and prone to change. When the temperature exceeded 300 °C, the E F of TCM decreased to −1.24 eV. The structure of TCM tended to stabilize and remained yellow. After immersion for 21 days, the protection efficiency ( Pi ) of TIAC for the metal reached 96.465 %, corrosion current density ( i corr ) was 6.501 × 10 −7  A cm −2 . This work combines thermochromism and corrosion resistance, and promotes the development in the design and application of multifunctional coatings.