Relationship between distinctness of image of organic coatings and texture of substrate sheets

Abstract

With the application of scanning electrical microscopy, surface profilometer and surface mapping microscopy, the two- and three-dimensional surface morphologies of the different substrate sheets, including cold rolling, hot dipped galvanised and electrogalvanised sheets, were characterised. The overlaid effect of paint on the surface texture of substrate sheets was analysed with the aid of low pass filtering. The specular gloss and distinctness of image (DOI) of organic coating were also measured, which are finally related to the texture of substrate sheets. The results showed that the DOI of organic coating on cold rolling, hot dipped galvanised and electrogalvanised sheets were ranked in descending order, which was identical to the tendency presented by the roughness and waviness of substrate sheets. A series of parameters was postulated under the consideration of DOI control for organic coating. In this study, the DOI score was >69% when R_a<0·86 μm, R_z<5·43 μm, R_pm<2·26 μm, S_m<78·81 μm and W_ca<0·411 μm.