(95e) Eis Evaluation of Corrosion Inhibitor-Based Epoxy Primer Coating on Aluminum Alloys

High Strength metals as well as metal alloys, such as aluminum alloys, are widely used as structural materials in aircrafts, ships and related industries. Though, these metal alloys are vulnerable to being damaged by corrosion, damage caused by corrosion failure has been identified as a major concern for the Department of Defense (DoD). It has a major impact in the US economy since more than eight billion dollars are been spent every year to inhibit corrosion damaged of aerospace materials. The weakening, cracking and degradation of oxidized metal may result in serious catastrophic accidents. Material deterioration caused by this phenomenon presents a risk at sight and a huge economical impact for industrial operations. This impact augmented our interest in innovation to carry out this research effort to evaluate pretreated and polyaniline-primed 2024 T3 and 7075 T6 aluminum alloys with non-destructive electrochemical impedance spectroscopy (EIS) for corrosion resistance performance when exposed to corrosive salt environment. Aluminum alloys must be pretreated with corrosion inhibitor prior to painting to prevent or reduce corrosion. EIS was used to evaluate the resistance of the coatings to corrosion in these alloys. Aluminum alloys specimens were exposed to room temperature having EIS cell attached to the surface containing a solution of 1% NaCl. The solution simulating salt water conditions was in direct contact with the metal surface. Periodically, these samples were taken out to observe the physical damages to the bare-metal/coated surface. With the EIS experimental data recorded using Gamry instrumental setup, charge transfer resistance and capacitance were obtained for the specimens as a function of exposure time. A 3-time constant equivalent electrical circuit model was employed to fit frequency dispersion data using non-linear statistical least square fit (NLLSF) method. Initial data did not reveal damage to the coated surface. Furthermore, EIS data did not show significantly changes in the impedance magnitude of the coatings. Uncoated and untreated metals demonstrated significant decrease in the impedance values with respect to exposure time. Keywords: aluminum alloys, salt-water, polyaniline mixed primer, EIS