Effect of Coating Thickness on Performance of Chromium Plating Steel Plate

Chromium plating steel plates containing chromium and chromium oxide on the surface of double cold rolling sheet by two-step method.The iron dissolved quantity and polarization curves of the plates were tested using spectrophotometer and electrochemical method. The corrosion resistance of the plates was evaluated by means of damp-heat test, salt-fog test and pasting filter paper method. The bonding strength of the plates with paint was studied by drop weight method, and the scanning electron microscopy was performed to observe the surface morphology. The results show that when the thickness of the chromium oxide coating was stable, with the increase of the thickness (weight per unit area) of the Cr plating coating, iron dissolved quantity decreased, damp-heat resistance and salt-fog performance enhanced, while the salt-fog resistance was poor. When the thickness of the whole chromium coating was stable, the bonding properties of the plates with paint increased with increasing the chromium oxide thickness. The weldability of the plates after electroplating Cr became poor.