Ionic Transport Through Metal-Rich Organic Coatings
Technical Report,01 Oct 2013,30 Sep 2015
Naval Air Warfare Center Aircraft Division Patuxent River United States
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Organic coatings are commonly used on aircraft and in the automotive industry to protect against corrosive environments. Although coatings are frequently used today, the mechanisms behind their protective nature are not fully understood. This paper investigates how metal particle volume MPV percent, solvent polarity, and resin molecular weight impact corrosion protection of metal-rich organic MRO coatings. Following design of experiments DOE and Taguchi methodologies, the three parameters investigated, along with their respective levels, were used to generate an orthogonal test matrix of coating formulations. Due to the brittle nature of the coatings, these formulations could not be stand-alone and were sprayed onto filter paper to lend structural support. Using a modified Hitorff cell, the nine independent formulations from the orthogonal matrix were tested for pH and chloride ion concentration levels over time. As the corrosion protection of the coating decreases, chloride ion concentration will increase. Preliminary tests indicate that the effects of MPV percent, solvent polarity, and resin molecular weight can be measured using a modified Hitorff cell set-up, however, no trends can be determined from the data at this time.