Iron Corrosion in CO[sub 2]/Brine at Low H[sub 2]S Concentrations: An Electrochemical and Surface Science Study

The effect of at the parts per million level on the early stage of iron corrosion in 3 wt % NaCl solutions saturated with is investigated using electrochemical and surface science techniques. Small concentrations (5 ppm) have an inhibiting effect on corrosion in the presence of . At higher concentrations (up to 500 ppm), the corrosion rate is higher but below the -free case. The characterization of the iron surfaces after corrosion uses photoelectron spectroscopy and electron microscopy. For Fe exposed to -containing solutions, a sulfur peak (S 2p) appears at a binding energy of 162.1 eV, attributable to disulfide adsorption. The Fe peak attributed to Fe(II) at the surface shifts by about 1 eV in the presence of 5 ppm compared to the -free case due to bonding of Fe to S and O. At higher concentrations, the formation of a S-rich surface is indicated. Morphological changes are observed on the iron surface after exposure to -containing solutions. A thin protective film forms at 5 ppm , while at higher concentrations a thicker, more porous surface phase forms. A mechanism for corrosion inhibition of iron in different concentrations of in is proposed.