A Comparative Study of Different Electrolytes on Anodizing of 2024 Aluminum Alloy and Electrochemical Behavior of Anodized Film

Muhammad Kamran, Tahir Ahmad, Usaid Azhar, Dil Khurram, Bambang B. A. Wahjoedi, Rafiq Ahmad, Faraz Hussain

Abstract


Technical and economic considerations are the main reasons which provide more and more importance to utilize aluminum and aluminum alloys in industries like automotive and aerospace. Corrosion resistance due to naturally formed protective surface alumina film is an added benefit. To enhance this feature of aluminum anodizing was introduced. In the present work, different electrolyte compositions were used to obtain oxide coating on aluminum for its corrosion protection. The aluminum alloy samples were anodized in different concentrations of sulphuric acid, sulphuric/oxalic acid and sulphuric/acetic acid and processed at different voltages. It was observed that the coating thickness increases with increases in voltages. Barrier type film is formed with low concentration of acids while the crystalline type film appears with the high concentration of acids.  The barrier type coating is passive in nature and corrosion is controlled by anodic reaction resulting in lower corrosion rate with higher corrosion potential. While for crystalline type coating the corrosion is controlled by cathodic reaction and resulted in higher corrosion rate at lower corrosion potential. Low corrosion rates with higher polarization resistance (Rp) value obtained for anodized coating at higher operating voltage depicts the formation of porous film on the surface.

Keywords


Aluminum Alloy 2024, Anodizing, mechanical properties and microstructures, Tafel scan

Full Text: 184_JPIChE 44 (1) 2016 184_JPIChE 44 (1) 2016

Published by Pakistan Institute of Chemical Engineers (PIChE)

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