The Corrosion Behavior of Tantalum and Niobium in Hydrobromic Acid Solutions

Abstract

Abstract The corrosion behavior of tantalum and niobium in hydrobromic acid solutions free from or containing bromine has been studied. Using electrochemical and mass loss techniques, the corrosion behavior as a function of (1) temperature, (2) HBr concentration, (3) Br2 concentration, (4) electrode potential, and (5) exposure time has been examined. From the measured rest potentials and steady-state polarization curves, it can be said that both metals are passivated in HBr solutions ranging in concentration up to the azeotropic composition of 47 weight percent (wt%) and to temperatures as high as 124 C. The corrosion rate of tantalum determined by mass loss testing in a hydrogen-bubbled 47 wt% HBr solution at 124 C was less than 2 milligrams per dm2 and day (mdd), and that of niobium at 100 C was ∼20 mdd. The corrosion rates of both metals in hydrogen-bubbled HBr solutions tended to decrease with decreasing temperature and HBr concentration and with increasing exposure time and electrode potential. The p...