Research Of Mechanism To Plating Defect On Tinplate Surface And Prevention Measures

The white spot defect on the coating surface is the main factor to affect the coating quality. This paper is about the research of the mechanism to the white spot on tinplate surface and the prevention measures in high-speed sulfuric acid tin plating process. In addition of the effect the surface appearance, the corrosion resistance of tinplate has been seriously affected by white spot defect too.The defect is studied by scanning electron microscope, energy spectrum analysis. The preliminary determination of white point is due to insufficient plating.The effect of electroplating process condition is researched by the Hull cell experiment. It is found that the solid impurity and ionic impurities in plating solution will affect the plating coating by simulating experiment. The solid impurity is tin clay, and the ionic impurities is mainly Fe+ and Cl-. The result show that when the density of the impurities in fluid rise up to the level, the coating quality become worse and worse,specially lead to plating leakage. Besides, strip steel substrate surface unclean is another important reason may cause the defect. It is Including the surface oil, oxides and rubber adhesion. If these impurities are not totally cleaned, some white spots would come out on the tinplate.