NITROGEN TETROXIDE CORROSION STUDIES

Abstract

Abstract : The purpose of this investigation was to determine quantitatively the corrosive effects of nitrogen tetroxide on mild steel, aluminum, stainless steels, and titanium. This was done under static conditions at six water concentrations up to 3.2 wt percent and four temperatures up to 74 degrees C. The corrosion rates under dynamic flow conditions were also investigated. The corrosion of carbon steel (ASTM A-285 Grade C) and aluminum (5086) was less than 0.5 mil per year in nitrogen tetroxide containing up to 0.21 wt percent water at 74 degrees C, increasing to 50 mils per year at 3.2 wt percent water and 74 degrees C. Negligible corrosion was observed under severe conditions with stainless steel (304-L) and titanium 75A and 6A1-4V) whereas high strength corrosion cracking was observed in tests of carbon steel, high strength steel or aluminum in nitrogen tetroxide containing 0.1 and 1.6 wt percent water at 49 degrees C. Significiant corrosion of stainless steel (304-L) occurred in the presence of Teflon. Dynamic tests showed no significant corrosion of 304-L and PH15-7 Mo stainless steels and average rates of 0.05 mils per year for aluminum and 0.33 mils per year for carbon steel after 205 hours exposure to commercial nitrogen tetroxide flowing at velocity of 10 ft per second at 30 degrees C.