Preparation Method and Its Properties of a Water-Based Chromium-Free Dacromet Coating

A kind of water-based chromium-free Dacromet coating was prepared on the surface of low carbon steel workpiece by using flake aluminum powder and zinc powder as fillers, silane coupling agent KH-560, boric acid and composite dihydrogen phosphate as film-forming materials. The surface morphology, composition, adhesion and corrosion resistance of the coating were examined by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), neutral salt spray test and electrochemical test. The results showed that the prepared water-based chromium-free Dacromet coating had good stability, and the coating did not change under the condition of 60℃ and 48 h. The surface of the chromium-free water-based coating after coating was uniform and smooth without obvious defects. After 600 h neutral salt spray test, there was no red rust on the surface of the coating. The self-corrosion potential of the water-based chromium-free Dacromet coating was negatively shifted, and the corrosion current was reduced by an order of magnitude, indicating that the corrosion resistance of the coating sample was improved, and the coating had good protective performance.