The electrochemical behavior of iron in H~2S-containing H~2SO~4 solutions has been studied by polarization curve method. The stable adsorption orientation and optimal adsorption distance of H~2S and HS^- on the crystal plane of iron at cathodic and anodic potential were determined by CNDO/2 method. By calculating the total energy, binding energy and net charge distribution of the absorptives, the adsorption behavior of H~2S and HS^- on the crystal plane of iron and the bonding state between iron and H~2S/HS^- at cathodic and anodic potential have been investigated. The following were inferred from the above results. At anodic potential, the adsorption of large amounts of HS^- on the crystal plane of iron in parallel direction through sulfur atom, which transferred the most of negative charge from HS^-, promoted the dissolution of iron. While at cathodic potential, the adsorption of small amounts of H~2S on the crystal plane of iron in parallel direction through hydrogen atom and the negative charge transfer from iron to hydrogen atom in H~2S interacting with iron promoted the evolution of hydrogen. The experimental results are satisfactorily explained with the above theoretical calculation.

Key words: HYDROGEN SULFIDE, CORROSION, IRON, CNDO APPROXIMATION, CORROSION TEST, ADSORPTION, ELECTROCHEMICAL PROCESS