51312-01274-Chrome-free self-healing protective coating for AA2024 in chloride containing solution

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Product Number: 51312-01274-SG

ISBN: 01274 2012 CP

Author: Abdel Salam Hamdy

Publication Date: 2012

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Chrome-free self-healing protective coating for AA2024 in chloride containing solution Abdel Salam Hamdy1 2 I. Doench1 and H. Möhwald1(1) Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany. Phone: (+49) 331 567- 9448 Fax: (+49) 331 567- 9202Email: asalam85@yahoo.com (2) Center of Research Excellence in Corrosion King Fahd University of Petroleum & Minerals Dhahran 31261 Saudi Arabia Abstract This paper aims at designing of a simple corrosion resistant vanadia based chemical conversion coating as alternative to the commonly used process involving toxic hexavalent chromate for high strength AA2024 alloy. The proposed coating is environmentally acceptable as a diluted vanadate solution was used at room temperature for a short treatment time. The effect of vanadia solution pH and the alkaline etching time prior to vanadia treatment was investigated in 3.5% NaCl using different electrochemical techniques such as electrochemical impedance spectroscopy linear polarization and cyclic voltammetry. Results showed that vanadia coatings prepared by dissolving 10 gram of vanadate salt per liter at the neutral pH (about 7) have proven to offer the best inhibition to localized corrosion after one week of immersion in chloride containing solution. The optimum alkaline etching time prior to vanadia treatment was also measured as a function of corrosion inhibition characteristic. A vanadia based surface treatment of self-healing characteristics prepared by simple industrially-applicable free immersion technique was proposed. The autonomic healing concept was investigated using AFM XPS SEM-EDS and macroscopic images.