The surface and electrochemical analysis of permanganate based conversion coating on alclad and unclad 2024 alloy

Yoganandan, G and Balaraju, JN and William Grips, VK (2012) The surface and electrochemical analysis of permanganate based conversion coating on alclad and unclad 2024 alloy. Applied Surface Science, 258 (-). pp. 8880-8888. ISSN 0042-207X

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Abstract

In the present investigation permanganate based conversion coating (PCC) was developed on AA 2024 alloy using alkaline bath containing Mn/Mo oxyanions. Conversion coating was formed on alclad (APCC) and unclad (UPCC) aluminium alloys by simple immersion method. Surface morphology of the APCC and UPCC specimens exhibited smooth and mud-crack patterns respectively. Elemental analysis showed the presence of higher amounts of Mn (5–6 wt.%) and Mo (0.3 wt.%) on UPCC. Raman and XPS analysis showed the presence of compounds such as MnOx (Mn3O4 and Mn2O3), MnO2, KMnO4, MoOx, MoO2, MoO3/polymolybdate on both coating surfaces. The corrosion current density (icorr) values obtained for both coated surfaces were less than 1 �A/cm2. However, APCC specimen showed the lowest icorr value of about 0.05 �A/cm2 after 168 h of immersion in 3.5% NaCl. EIS studies revealed the higher charge transfer resistance (Rct) values for APCC specimen after 1 and 168 h immersion compared to UPCC. Coated specimens were also tested by continuous salt spray exposure (ASTM B117) with and without cross-hatch mark (‘X’) for about 750 h. Coating discoloration along with the presence of few corrosion products had been noticed on UPCC specimen after continuous salt spray expos

Item Type: Article
Uncontrolled Keywords: Permanganate conversion coating EIS Raman spectroscopy Corrosion Alclad unclad AA2024 alloy
Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
Depositing User: Users 10 not found.
Date Deposited: 30 Aug 2012 10:47
Last Modified: 18 Feb 2013 04:41
URI: http://nal-ir.nal.res.in/id/eprint/10870

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