Comparison of Corrosion Behavior of 1.4361 Si-Alloyed and 316 Austenitic Stainless Steels in Nitric Acid Based Propellant

Corrosion behavior of 1. 4361 high Si-alloyed austenitic stainless steel in red fuming nitric acid (RFNA) was compared with 316 SS by using linear and cyclic potentiodynamic polarization techniques، immersion corrosion test method and SEM observations. In addition، the inhibition effect of different concentrations of hydrofluoric acid (HF) on the corrosion behavior of the alloys was studied. The results obtained from electrochemical measurements، immersion test and SEM observations are in good agreement and indicate that HF is a good inhibitor against uniform and intergranular corrosion. A high initial corrosion rate of 16. 77 mpy was observed in absence of inhibitor، which was decreased to 0. 24 mpy with addition of 0. 6 wt% HF. Moreover، pitting potential at the same condition increases from 1. 57 to 2. 31 V (vs. Ag/AgCl)، indicating to improve the localized corrosion resistance with addition of HF inhibitor. Also، it is indicated that the Si alloying element، on one hand، leads to increase the intergranular corrosion resistance and، on the other hand، leads to reduce the general corrosion resistance. An initial corrosion rate of 1. 18 mpy was obtained for the 316 SS، lower than that of the 1. 4361 Si-alloyed SS.