Influence of Surface Roughness of Cold-rolled Steel Sheet Oncathodic Electrodeposition Coating

摘要

Cathodic electrodeposition paint coating has been widely used as a primary layer coating in the automotive industry.And steelmakers have improved the roughness of steel sheet with the textured temper mill to improve the paint adhesion.As the roughed steel sheet is not easy to be covered by paint,the roughness of steel sheet should be limited to balance the adhesion property and visual appearance quality of paint.In this work,the properties of cathode electrodeposition paint coatings on cold-rolled steel sheets with various roughness were tested and measured by roughness meter,cup drawing machine and impact testing machine.It was indicated that the Ra of paint film was less than 0.3μm when the Ra of steel substrate was between 0.6～1.3μm and an increase was seen with the increasing Ra of steel sheet.After the 5mm cupping test,the coatings of all samples remained intact without any cracks or flaking.When 50 kg·cm and 70 kg·cm impact force is used,no cracks,wrinkles or flaking can be seen on all samples,as the Ra of steel substrate increases,the increased impact resistance was observed.