Correlations between the volta potential and filiform corrosion on painted aa2024 aluminum alloy

Abstract

The susceptibility to filiform corrosion of painted AA2024 alloy has been widely demonstrated, but an analytical method to determine the filiform corrosion resistance is still under investigation. This work aims at analyzing the possible correlations between the chemical and electrochemical properties of coated AA2024 samples and their susceptibility to filiform corrosion. In particular, the different behaviors of three different primer coatings have been investigated. The work proposes a few hypotheses of possible correlations among the work function difference of the coated samples, the progress of the filiform corrosion and the barrier properties of the organic primers. The filiform corrosion resistance of the pretreated and primer-coated samples has been evaluated following the procedure proposed in the EN 3665:1997 standard. The results have been compared with multiple scanning Kelvin probe (SKP) measurements performed on the intact primers before the beginning of the accelerated test. The electrochemical characterization has been completed by means of electrochemical impedance spectroscopy measurements. The properties of the primer-metal interface have been investigated in order to find a direct correlation with the SKP results. A possible correlation between the work function difference measured on the intact sample and the resistance to filiform corrosion is proposed. Copyright ©2010 John Wiley & Sons, Ltd.