CORROSION OF TI-6AL-4V ALLOY AND 304L STAINLESS-STEEL IN LIQUID-NITROGEN OXIDES

Liquid dinitrogen tetroxide is normally stored in stainless steel tank s, whereas the mixed oxides of nitrogen, dinitrogen tetroxide plus nit ric oxide, may also be stored in titanium alloy vessels, This article presents new data on the corrosion of unstressed 304L stainless steel and Ti-6Al-4V by these rocket propellant oxidizers at 30 degrees C as a function of time at a surface-to-volume ratio of 6 cm(-1). The resul ts show that dry dinitrogen tetroxide (0.003 and 0.02-wt% water equiva lent) is the more corrosive medium towards both alloys: the iron oxida tion product dissolves more in dinitrogen tetroxide plus 3% nitric oxi de, whereas the titanium alloy corrosion products are more soluble in the NO-free medium, However, attack Is extremely limited in both oxidi zers, It Is finished after 550 days (and probably In less than 55 days ) In dinitrogen tetroxide and corresponds to the oxidation of a 30- to 40-Angstrom layer of alloy, In dinitrogen tetroxide plus 3% nitric ox ide only a fifth of the corrosion takes place, and then within a perio d of less than 50 days, The results depend substantially on the analys is of the key component metals (Al, Ti, V, Mn, Fe, Cr, and Ni) as dete rmined by state-of-the-art spectrometric methods.