Role of KMnO₄–NaF Treatment in Galvanic Corrosion Resistance of AA5083 Coupled to Steel

Abstract

The role of KMnO₄–NaF conversion treatment in the galvanic corrosion resistance of AA5083 aluminum alloy coupled to AISI 1045 carbon steel in synthetic seawater (diluted 100 times) was investigated. The 10 min-treated AA5083 was observed to reduce the period of high current density during the early stage of coupling and decrease the number of localized corrosion damages on the AA5083. The 10 min conversion treatment significantly reduced the electrode potential of bulk Al₆(Fe, Mn), and it was concluded that the Al₆(Fe, Mn) particles on the conversion-treated AA5083 no longer acted as a local cathode at the electrode potential when the AA5083 was in contact with AISI 1045 carbon steel. The decrease in cathodic activity of Al₆(Fe, Mn) was attributed to the removal of Fe from the surface film of Al₆(Fe, Mn), addition of Mn by the conversion treatment, and thickening of the film.

Mean number of localized corrosion damages on as-polished and KMnO₄–NaF conversion-treated AA5083 specimens after galvanic current measurements in synthetic seawater (diluted 100 times). The experiments were conducted three times, and the error bars indicate minimum and maximum values.