EFFECT OF HYDROGEN-SULFIDE ON AQUEOUS CORROSION OF COMMERCIALLY PURE AL-99.5

The effect of hydrogen sulfide (H2S) on the corrosion behavior of comm ercially pure aluminum (DIN Al 99.5 [AA 1050A]) in chloride (Cl-) solu tions containing carbon dioxide (CO2), bicarbonate (HCO3-), and copper ions (Cu2+) at 30 degrees C and 80 degrees C was investigated using n atural immersion corrosion tests, cathodic polarization, and scanning electron microscopy (SEM). The highest corrosion rates were observed i n solutions containing Cu2+ but with no H2S content because of copper deposition on the metal surface. Significant pitting occurred at 80 de grees C. With H2S in the solution, pitting corrosion was eliminated by removal of Cu2+ and other deleterious heavy-metal ion impurities from the solution in the form of insoluble sulfides. If H2S was introduced after the copper deposited on the aluminum surface, no inhibiting eff ect was detected at 30 degrees C, but a degree of inhibition still was observed at 80 degrees C, presumably because the deposited copper was converted more effectively into copper sulfide (CuS) at the higher te mperature.