Anti-Corrosion and Morphological Analysis of a Conversion Coating Based on Nanoceramic Hexafluorozirconic Acid on a Steel Substrate

Eivaz Mohammadloo, H.; Sarabi, A. A.; Sabbagh Alvani, A.A.; Sameie, H.; Salimi, R.

Anti-Corrosion and Morphological Analysis of a Conversion Coating Based on Nanoceramic Hexafluorozirconic Acid on a Steel Substrate

Authors

¹ Department of Polymer Engineering & Color Technology, Amirkabir University of Technology

² Department of Polymer Engineering and Color Technology, Amirkabir University of Technolog

³ Color and Polymer Research Center, Amirkabir University of Technology

Abstract

In this research, a nanoceramic hexafluorozirconic acid based conversion coating free of phosphate salts was investigated. The effect of practical parameters such as solution pH, temperature and dipping time on coating morphology and anti-corrosion resistance of coating was evaluated. Anti-corrosion resistance of so-called nanoceramic conversion coating on cold rolled steel (CRS) substrates in different solution pH, temperatures and immersion’s time, utilizing DC Polarization was studied. The conversion coating which was formed at dipping temperature of 20 °C, pH=5 and immersion’s time of 60 seconds had the best anti-corrosion resistance. The morphology of the conversion coating surface formed at different pH was investigated using Atomic Force Microscopy (AFM). Images obtained from the microscope indicate that the conversion coating which formed in pH=5 was more consistent and had finer aggregates in comparison with pH=4.25 coating. Field Emission Scanning Electron Microscopy (FE-SEM) of conversion coating formed in 20 and 40 °C indicated that surface of conversion coating with higher temperature had micro cracks and was not uniform , also nodules on the scale of tens of nm (40–60 nm) in size, was observed on the surface.

Keywords