Commercially available vapor phase corrosion inhibitors were evaluated to determine their corrosion inhibition for aluminum alloys in a water-ethylene glycol (C2H6O2) mixture. When the temperature exceeds 80°C, ethylene glycol can decompose into organic acids. The resulting acid environments cause severe corrosion of aluminum alloys. Electrochemical and constant immersion tests were carried out to study the effects of several inhibitors. The corrosion behavior was studied at multiple temperatures. Corrosion inhibitor VCI-A at 2.5% dosage showed excellent corrosion protection. It maintained a steady, low corrosion rate during long term exposure by neutralizing pH and forming a hydrophobic film. VCI-B inhibitor, also showed the ability to reduce the corrosion rate of aluminum in ethylene glycol solutions. However, due to its high pH chemistry, the effective dosage should be maintained at 2.5% to avoid any potential increase in pH that can promote localized corrosion or under-deposit corrosion attacks. The results of this investigation demonstrated that both inhibitors can lower the corrosion rate in water-ethylene glycol solutions by neutralizing pH and forming stable films.
The efforts to lower automotive component weight to make cars more fuel efficient has increased the demand for aluminum alloys. In these applications, substantial amounts of heat are generated due to engine combustion, making it necessary to cool the engine systems. Metals in an engine application will rely on coolant to transfer heat. Corrosion behavior is another consideration for metals. Aluminum alloys, similar to the metals they are replacing, are sensitive to corrosion, especially in an aqueous alkaline environment. The breakdown of the protective surface film of aluminum oxide when exposed to hydroxyl ions (OH−) makes it more susceptible to corrosion. Ethylene glycol (EG) is a chemical compound that has an alcohol with two -OH groups. [1] One of the main uses for ethylene glycol is in the automotive industry as an antifreeze and coolant because it has a much lower freezing point than water. Ethylene glycol (C2H4(OH)2) in the car's cooling system neutralizes temperature by removing and circulating heat. The temperature of the engine coolant can reach between 160°C to 200°C. EG decomposes at high temperatures into organic acids (glycolic, formic, acetic, and oxalic acids) which creates a corrosive environment for metals and can cause severe pitting corrosion at high temperatures. [2,3]
