Abstract: In this work，white spot defection on phosphating membrane has been researched. When automobile body passes through the pretreatment line of painting workshop，the defection occurs on cold-rolled steel substrate. Through investigations，experiments and SEM analyses，we find that the position of white spot on the phosphating membrane almost without any phosphating crystallizations attached. This phenomenon is owing to the rust corrosion，which is formed during washing process，has been dissolved firstly in the phosphating tank. Then the normal phosphating reaction on the cold-rolled steel substrate has been delayed，which result to the specific position on the substrate almost has no phosphating crystallization. Subsequently，through adding a certain amount of degreasing agent to rinse tank，the phosphating membrane white spot defection on cold-rolled steel has been successfully resolved.

Key words: painting, pretreatment, cold-rolled steel, phosphating membrane, white spot

摘要： 研究一次涂装前处理冷轧板上的磷化膜“白点”缺陷，通过对工序进行排查、设计验证试验，应用扫描电镜、扫描电镜能谱仪等对“白点”问题进行分析。研究发现：冷轧板上的磷化膜“白点”部位几乎无磷化膜附着，金属光泽的基材与周围银灰色的磷化膜形成颜色反差，表现为“白点”。其根本原因是由于车身经过水洗后冷轧板表面发生锈蚀，附着在板材表面的氧化铁在磷化槽内先被酸解，延迟了磷化反应上膜时间，导致锈蚀区几乎无磷化膜覆盖。通过对预水洗添加一定量的脱脂剂，成功解决了车身冷轧板上的磷化膜“白点”缺陷。

关键词: 涂装, 前处理, 冷轧板, 磷化膜, 白点

CLC Number: 

• TQ639. 8