Research On Formation Mechanism Of Smudge On Tinplate Surface And Prevention Measures

Smudge is the main factor to affect the coating quality in the actual production, it scatters on the surface of the tinplated steel. Not only the appearance but also the combining power between tin coating and passivation film are affected by smudge. This paper is about the research on formation mechanism of smudge on tinplate surface and prevention measures in the process of tinplating.The morphology and composition of smudge is first studied by scanning electron microscope analysis, chemical analysis, infrared spectrum analysis and X-ray diffraction analysis. The cause of smudge is initially estimated according to its morphology and composition. It has been clear about that the sludge in the plating solution, reflowing process, the impurity in the passivation solution and rubber roller are the main factor. And this paper mainly focuses on the study of these several factors. The influence of sludge on smudge is studied with the electroplating experiment of different sludge concentration. It is found that the sludge in the plating solution deposit to the coating together with tin. With the simulated experiment of reflowing and passivation solution soak, it is found that the smudge occurs on the surface of tinplate coating after reflowing, and the amount of smudge increases with the increasing concentration of sludge in the plating solution. And the impurity in the passivation solution like Cl-, Mg2+, Ca2+lead to the generation of smudge to varying degrees. Besides, the rubber roller used in the tinplating line is also an important causing factor due to its abrasion and the abrasion of strip steel surface caused by the sliding friction between rubber roller and strip steel. The prevention measures are developed accordingly in the actual production with the analysis of the affecting mechanism of smudge formation by these factors, to effectively control the generation of smudge.