Investigation of fluoacid based conversion coatings on aluminum
By Deck, Philip D; Moon, Molly & Sujdak, Richard J
Published in Progress in Organic Coatings
1998
Abstract
Conversion coatings on metals enhance paint or lacquer adhesion and promote corrosion resistance. Traditionally, these conversion coatings were based on chromium chemistry. In recent years, formulations based on fluotitanic or fluozirconic acid and polymer have demonstrated performance on a par with chromium-based treatments. The choice of fluoacid and polymer in the treatment has a strong impact on coating performance. The impact of pretreatment composition was demonstrated for aluminum extrusion processes. Electrochemical investigation, including linear polarization and electrochemical impedance spectroscopy, was used to differentiate corrosion resistance among the various treatments. Scanning electron microscopy, grazing angle infrared spectroscopy, and X-ray photoelectron spectroscopy were used to elucidate chemical composition of the treated aluminum surfaces.