The effects of the steel’s surface quality on the properties of anti-corrosion coatings

Abstract

The requirements of painted vehicle construction in terms of corrosion resistance apply not only to cars but also to heavy duty lorries, trucks and agricultural machinery. Phosphating is the most commonly used method for the pre-treatment before painting of ferrous metals in the vehicle manufacturing industry. The task of the phosphate layer between the metal surface and the paint is to protect the metal from corrosion under the paint film and promotes the adhesion of the paint film to the metal substrates. In this study the zinc phosphate conversion layer was deposited onto the steel surfaces from a bi-cationic (nickel-free) phosphating bath by dipping using identical technological parameters. The developed crystal structure and morphology was examined in terms of surface roughness and blasting quality of the metal. The surface quality of the metal was tested by digital light microscopy (LM), and the structure of phosphate coating was investigated by scanning electron microscopy (SEM).