Investigation of the Localized Corrosion Resistance of 4044 Aluminum Alloy in Acid Chloride and Neutral Chloride Solutions

摘要

The corrosion resistance of 4044 aluminum alloy (4044AL) in acid chloride and neutral chloride solutions at 0.25–1.75% NaCl concentration was studied with potentiodynamic polarization technique, optical microscopy and open-circuit potential measurement. Variation of Cl_(?)ion concentration had limited influence on the corrosion rate values of 4044AL in both test solutions; however, the corrosion rate values of 4044AL in the acid chloride media are significantly higher than values obtained from the neutral chloride solution due to the combined debilitating action of $${ext{SO}}_{4}^{2 - }$$ SO 4 2 - and Cl_(?)ions in the acid chloride. Passivation behavior in the acid chloride media was completely absent compared to the neutral chloride solution where the passivation range extended across wide potentials before breakdown at the transpassive regions of the polarization plot due to localized corrosion reactions. Significant cathodic potential shift of 4044AL polarization plots and open-circuit potential was observed after 0.25% NaCl in the neutral chloride solution signifying dominant cathodic electrochemical reactions associated with localized corrosion on the steel surface. Morphological representations of the corroded 4044AL surface from 0.25 to 1.75% NaCl concentration showed the presence of extensive pitting and intergranular corrosion on the alloy from the neutral solution compared to general surface deterioration and superficial localized corrosion on the alloy from the acid chloride media which corroborate the extended time it took the alloy to achieve thermodynamic stability in the neutral chloride solution.