Impact of Organic Coatings on Corrosion of Aluminum Alloys
Mike Hurley and Daryl Butt
In the commercial and military aviation field corrosion is an unavoidable and potentially hazardous fact of life. Aluminum alloys are generally among the best options for use in these applications due to their relatively low cost and desirable material properties. The reliability and longevity of the various aerospace components made from these materials are often determined by the rate at which they corrode. It is therefore important to understand the critical factors which influence corrosion, including the effectiveness of any applied protective coating. Three alloys were chosen for this study; Al 2024 T3, Al 2024 T0, and Al 1100. Electrochemical experiments have been undertaken to characterize the baseline corrosion behavior and influence of ionic transport across an epoxy primer coating system to the underlying metal-coating interface. The samples were first characterized to determine microstructural differences between the alloys, followed by electrochemical corrosion testing of both epoxy coated and un-coated samples. Coated and uncoated samples were placed into a three electrode cell designed to hold one surface submerged in a solution of water and salts at varying pH. Results from baseline testing revealed the influence of alloy composition on corrosion behavior as a function of pH. Additionally, results from testing coated samples in similar conditions will aid in determining the effect of the epoxy primer coating on the overall corrosion behavior. The results from this work will be used to support a concurrent effort to model the effect of solution composition on the corrosion rate of coated aluminum alloys.