EVALUATION OF SEALING METHODS FOR ANODIZED ALUMINUM-ALLOYS WITH ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS)

Al alloys 2024, 6061 and 7075 have been anodized in II,SO, solutions o f two different concentrations and sealed in either boiling water or s olutions of nickel acetate, cerium acetate or yttrium acetate at two d ifferent temperatures, The same aluminum alloys were anodized in Boein g's Boric-Sulfuric Acid Anodizing (BSAA) process and sealed in a dilut e chromate solution car boiling water. The properties of the sealed ox ide layers and their changes during exposure to 0.5 N NaCl were monito red using EIS, From the impedance spectra, the pore resistance, R-po, the specific admittance, A(s) were determined as a function of exposur e time extending up to 14 days. At the end of exposure, the anodized s urfaces were examined by visual observation to determine the total pit ted area, A(pit), Sealing in cerium acetate solutions produced samples with a corrosion resistance comparable to that determined for sealing in nickel acetate.