Effect of Process Parameters on Corrosion Resistance and Microstructure of Vanadium Conversion Coating on Aluminum ۲۰۲۴ Alloy

In this research, a vanadium based conversion coating on the aluminum ۲۰۲۴ alloy was applied. The effects of the most important process parameters such as pH (۳, ۳.۵, ۴, ۵, ۶, ۷), immersion time (۱۰, ۱۵, ۲۰, ۲۵, ۳۰ minutes), sodium vanadate concentration (۵, ۷/۵, ۱۰ gr/lit) and solution temperature (۱۵, ۲۵, ۳۵, ۴۵ ° C) on corrosion resistance and the morphology of the conversion coating were evaluated. Obtained results from DC (Direct polarization) and EIS (Electrochemical Impedance Spectroscopy) revealed that coated sample at the salt concentration of ۱۰ gr/lit, pH equal to ۴, room temperature and immersion time of ۲۵ minutes had the highest anti-corrosion performance. Corrosion current density and polarization resistance for untreated substrate are ۲.۲۸ μA/cm۲ and ۲۶ kohm.cm۲ respectively. These values for optimized vanadium conversion coating are ۰.۱۳ μA/cm۲ and ۱۴۷ kohm.cm۲. The results of scanning electron microscope showed the formation of uniform convergence of vanadium conversion coating on the aluminum ۲۰۲۴ alloy. Based on the results of energy dispersive X-ray spectroscopy of coated sample at optimal conditions, vanadium conversion coating contains about ۳ wt. % of vanadium.

کلیدواژه ها:

Corrosion ، Vanadium conversion coating ، Electrochemical impedance spectroscopy ، Direct polarization ، Scanning electron microscope ، Energy dispersive X-ray spectroscopy ، Aluminum ۲۰۲۴ alloy ، خوردگی ، پوشش تبدیلی وانادیوم ، طیف سنجی امپدانس الکتروشیمیایی ، پلاریزاسیون جریان مستقیم ، میکروسکوپ الکترونی روبشی ، طیف سنجی پراکنش انرژی اشعه ی ایکس ، آلومینیوم ۲۰۲۴.