CNDO/2 study on the action of hydrogen sulfide in the corrosion of iron insulfuric acid solution

The electrochemical behavior of iron in H2S - containing H2SO4 solutions ha s been studied by polarization curve method. The stable adsorption orientat ion and optimal adsorption distance of H2S 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 H2S and HS- on the crystal pla ne of iron and the bonding state between iron and H2S/HS- at cathodic and a nodic potential have been investigated. The following were inferred from th e above results. At anodic potential, the adsorption of large amounts of HS - on the crystal plane of iron in parallel direction through sulfur atom, w hich transferred the most of negative charge from HS-, promoted the dissolu tion of iron. While at cathodic potential, the adsorption of small amounts of H2S on the crystal plane of iron in parallel direction through hydrogen atom and the negative charge transfer from iron to hydrogen atom in H2S int eracting with iron promoted the evolution of hydrogen. The experimental res ults are satisfactorily explained with the above theoretical calculation.