The corrosion rates for Udimet 500 in a variety of sodium sulfate-magnesium sulfate-vanadium pentoxide slag compositions were measured electrochemically at temperatures varying from 800 to 950". The weight ratios of the elemenis, sodium to vanadium and magnesium to vanadium, were defined for acceptable corrosion rates. The effects of sodium level and temperature are discussed. A simple rationale for the effectiveness of magnesium as a corrosion inhibitor is presented.

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A technique has been developed for evaluating the activity of antioxidants in rubber samples using a differential thermal analyzer. Results were obtained at 300 p.s.i. and atmospheric pressure, the former being apparently more significant than the latter. Evaluations were carried out on eight rubber samples which contained either an antioxidant of the phosphite, amine, or phenol type or no antioxidant. The activation energies and reaction orders were also estimated for the oxidation under 300 p.s.i. oxygen. Techniques used in this work evaluate only the free radical trapping ability of the antioxidant and are not effective for peroxide scavenging-type antioxidants. Oxidation of rubber at high temperatures proceeds by several paths simultaneously.

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Excellent correlation exists between a high-pressure differential thermal analysis (DTA) technique and the conventional tensile strength and ultimate elongation measurements used for evaluating antioxidant activity in rubber samples. Tensile strengths and ultimate elongations were measured on cured natural rubber samples aged for 96 hours in a bomb under 300-p.s.i. oxygen at 7OoC. The DTA data were obtained on the same series of samples subjected to a variety of curing and aging conditions. DTA test data from samples containing the same group of antioxidants but prepared from a high Mooney type 1500 styrenebuitadiene latex also correlated with the tensile strengths and ultimate elongations of the natural rubber samples. The antioxidants consisted of five phosphites, folur amines, and one phenol. Since tensile strength and ultimate elongation after oxygen aging are a function of antioxidant effectiveness, the DTA method can be assumed to be a reliable means of rapidly evaluating antioxidants.