Study of the influence of copper on zirconium-based coatings

Abstract

Zirconium oxide-based conversion coatings are nickel free alternatives to phosphate coatings. By focusing more on ZrCC we will be able to create a thin film technology that is environmentally friendly, cost effective and has comparable corrosion resistance and paint adhesion for ferrous and non-ferrous substrates. Here a significant body of work exists, concerning the role of copper on zirconium-based coating on three different metal bases; aluminium alloy, cold rolled steel and hot galvanized steel with a film thickness of 18-22 nm. The influence of Cu on the deposition mechanism was studied by using different amount of concentration added inside the conversion coating bath (4, 10 and 20ppm). This dissertation begins with understanding the advantages of zirconium-based coating and followed by explanation of the required steps according to the customer demand in industrial scale. Statistical analysis of X-ray Fluorescence results demonstrated an increase of deposition of Zr when more Cu is added inside the bath especially on hot galvanized steel. To make a definite understanding on the electrochemical process that occurs, conical mandrel test is used to examine the paint adhesion The effect of Zn was investigated to note the optimum concentration of Cu that can create a sufficient protective layer for all metal substrates even with Zn contamination. Hexafluorozirconic acid is studied to explore other alternatives to substitute the commercial products used throughout the project.