Preparation of Molybdate-Permanganate Conversion Coating for Corrosion Resistance

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Pisut Jirasirilert
Napachat Tareelap
Choochat Nitipanyawong


This work aims to prepare, chrome-free, molybdate-permaganate coatings to protect electrogalvanized steel (EGS) from corrosion in automotive and appliances industries. The coatings were prepared by immersion EGS in a mixture solution of sodium molybdate (Na2MoO4 2H2O) and potassium permanganate (KMnO4) at a molar ratio of 1:0.2 and 1:1 for 1, 1.30, 2 and 5 minutes at temperature of 50oC. The pH used was 3 and 4. The results stated that the superior corrosion resistance molybdate-permanganate coating prepared from solution having Mo:Mn molar ratio of 1:0.2 at pH 4 had corrosion resistance similar to that of commercial chromium(III) conversion coating. Moreover, it delayed corrosion onset longer than commercial chromium (III) conversion coating because of its low anodic and cathodic reactivities together with a crack-free surface.


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