Cerium based conversion coatings are done on the four galvanized (zinc plated) steel sheet in order to replace conventional chromate conversion coatings. Hydrogen peroxide and colloidal silica are employed to enhance the corrosion protection property. Electroplated zinc, hot dip zinc and electroplated zinc nickel steels are used as substrates. Samples are simply dipped into cerium conversion coating solutions at room temperature and oven baking process is followed. The corrosion protection property of treated samples are evaluated using by electrochemical techniques and corrosion accelration test (ASTM B-117). The characteristics of coating layer are done by SEM and SAM techniques. The cerium conversion coating on the zinc nickel based samples shows the excellent corrosion protection property comparison with electroplated and hot dip zinc steel. The cerium-based conversion coating layer is composed of Ce-O-C-Si complexes. All of treated galvanized samples passed 100 hrs without any white rust in the salt spray chamber. The treated EN showed the excellent corrosion resistance property. The cerium-based conversion coating used in this study has a high potential when applying it any galvanized steel without pre-treatment.
展开▼
