Electrode polarization studies in hot corrosion systems. Progress report, 1 June 1979-31 April 1980

Work on the following discrete tasks is reported: Electrode Polarization Studies in Molten Sodium Carbonate: A comprehensive set of tests has been performed on iron, nickel, and types 304 and 316 stainless steel in gas mixtures of controlled CO, CO/sub 2/, H/sub 2/, and H/sub 2/S pressures at a total pressure of one atmosphere and in a temperature range of 900 to 1000/sup 0/C. The polarization curves thus derived have been reduced to a set of empirical kinetic constants via computer modelling. Gas/Metal Reactions in Mixed Oxidants: Oxidation of iron in gas mixtures of controlled P/sub CO/, P/sub CO//sub 2/, P/sub H//sub 2/ and P/sub H//sub 2//sub S/ at a total pressure of one atmosphere and a temperature of 900/sup 0/C has been studied. In the P/sub S//sub 2/ and P/sub O//sub 2/ ranges employed sulfide scales were formed; P/sub O//sub 2/ influenced the short term sulfidation kinetics. Specimen geometry was seen as a significant factor influencing long term kinetics. Liquid Line Corrosion: A reproducible corrosive attack is seen at the metal/molten carbonate/gas phase junction. This attack can be quantitatively evaluated and explained in terms of a diffusion model. Evaluation of Reaction Kinetics from Polarization Data (addendum): previous modelling procedures have been expanded to include one or more anodic reactions displaying passive behavior.