Thermogravimetric thin aqueous film corrosion studies of alloy 22; Calcium chloride solutions at 150 deg C and atmospheric pressure

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Thermogravimetric thin aqueous film corrosion studies of alloy 22; Calcium chloride solutions at 150 deg C and atmospheric pressure

Hailey, P. / Gdowski, G.

The extent of reaction of alloy 22 with limited amounts of aqueous calcium chloride (CaCl2) was investigated. Alloy 22 is a highly corrosion-resistant nickel-chromium-molybdenum-tungsten alloy. Specimens were polished to a mirror finish prior to aerosol salt deposition. An aqueous film was formed on the specimen surface by deliquescence of deposited CaCl2 at 150 deg C and 22.5% relative humidity (RH). The reactant gas was a continuous flow of purified humidified laboratory air. The reaction progress as a function of time was continuously measured in-situ by a microbalance. An initial weight gain due to CaCl2 deliquescence was observed. A steady weight loss was observed over the next 24 hours, after which no further weight change was apparent. During the period of weight loss, white precipitates formed and the specimen surface became visibly dry. Post-test analyses indicated that the precipitates consisted of calcium, chloride, and oxygen.