The effect of H2 S at the parts per million level on the early stage of iron corrosion in 3 wt % NaCl solutions saturated with CO2 is investigated using electrochemical and surface science techniques. Small H2 S concentrations (5 ppm) have an inhibiting effect on corrosion in the presence of CO2. At higher H2 S concentrations (up to 500 ppm), the corrosion rate is higher but below the H2 S -free case. The characterization of the iron surfaces after corrosion uses photoelectron spectroscopy and electron microscopy. For Fe exposed to H 2 S -containing solutions, a sulfur peak (S 2p) appears at a binding energy of 162.1 eV, attributable to disulfide (S2 2-) adsorption. The Fe 2 p3/2 peak attributed to Fe(II) at the surface shifts by about 1 eV in the presence of 5 ppm H2 S compared to the H2 S -free case due to bonding of Fe to S and O. At higher H2 S concentrations, the formation of a S-rich surface is indicated. Morphological changes are observed on the iron surface after exposure to H2 S -containing solutions. A thin protective film forms at 5 ppm H2 S, while at higher H2 S concentrations a thicker, more porous surface phase forms. A mechanism for corrosion inhibition of iron in different concentrations of H2 S in CO2 /brine is proposed.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry