Corrosion Prevention by Applied Coatings on Aluminum Alloys in Corrosive Environments

In this study, the corrosion resistance of selected aluminum alloys with various combinations of commercial coatings was investigated using the Tafel electrochemical method in water and simulated salt water environments. The microtopography of the surfaces of the metals and applied coatings was tested using atomic force microscopy (AFM) and optical microscopy (OM) analysis. The combination of an environmentally friendly electrodeposited ceramic coating with a primer and topcoat, which results in a chromium-free coating, exhibited a higher polarization resistance and a lower corrosion rate than the traditional chromate conversion coating combination. Coating defects and pores, which were revealed by the AFM images, were demonstrated to contribute to higher corrosion rates.