Comprehensive performance test and analysis of graphene-enhanced chromium-free Dacromet coating

Abstract

Abstract The proposed work aims to improve the comprehensive properties of the composite coating by adding different content of graphene into the coating solution. Firstly, the formulation of the coating solution was determined by the L16(45) orthogonal test. Secondly, the conventional properties of the coating were tested using the optical microscope and micro-vickers hardness tester. Thirdly, the corrosion resistance of the coating was tested by the rapid ammonium nitrate corrosion test, immersion test, and neutral salt spray test. The changes of the microstructure and composition of the coating before and after corrosion were observed and analyzed using the scanning electron microscope, energy dispersive spectrometer, X-ray diffractometer, and Raman spectrometer, and the Tafel polarization curves and electrochemical impedance spectroscopy of the composite coatings with different graphene contents were tested by electrochemical experiments. The results show that the hardness of the coating increases with the increase in the content of graphene. Graphene intercalates between zinc and aluminum powders in a flaky structure, which reduces the appearance of voids and enhances the protection of chromium-free Dacromet coatings, slows down the penetration of electrolyte solutions and effectively slows down the penetration of corrosive media. The addition of a small amount of graphene can increase the corrosion potential and decrease the corrosion current density of the chromium-free Dacromet coating, the Nyquist low frequency of the coating is higher in the same period and the salt spray resistance of the coating is the best.