Effect of Barrel Plating Velocities on Properties of Mechanical Plated Zn-Al Composite Coating

The plating process has a great influence on the appearance and corrosion resistance of the coating. In order to deeply understand the effect of barrel plating velocity on Zn-Al composite coating, thecomposite coatings were prepared on Q235 steel substrate by mechanical plating equipment at three different velocities of 1.047 m/s, 1.309 m/s and 1.571 m/s,respectively. The surface and cross section morphology of the coatings were characterized by scanning electron microscopy（SEM）, the bonding strength of the coating was observed by optical microscopy, the hardness of the coating was tested by Vickers hardness tester, and the specimen was tested by electrochemical analysis instrument. The results show that when the velocity is 1.047 m/s, the density area of the coating is small and the thickness of the coating is lower than that of the pre-coating; when the velocity increases to 1.309 m/s, the coating is flat, with many dense areas, and the coating hardness increases and the hardness of each point is uniform; when the velocity increases to 1.571 m/s, the coating thickness is uniform,and there is no peeling off at the intersection of scratches; with the increase of the barrel plating velocity, the coating corrosion potential is positive shift, the corrosion current density reduces, and the corrosion resistance is enhanced.