Effects of Hydrogen Halides On Anodic Polarization of Stainless Steel

The anodic polarization of stainless steel in 10 moles/liter sulfuric acid with various concentrations of HF, HCl and HBr has been investigated. At sufficiently high concentrations all of these hydrogen halide ions make it more difficult to establish and maintain passivity. They did not change the potential at which passivation was established, but they narrowed the passive potential range by increasing the potential at which breakdown occurred. They all accelerated the decay of passivity when the applied currents were interrupted. Effective protection from corrosion can still be obtained in these systems. In the presence of 1 mole per liter hydrogen fluoride, there was a substantial increase in current to maintain passivity without any corresponding loss of metal.