Experimental investigations on iron corrosion products formed in bicarbonate/carbonate containing solutions at 90°C

The influence of initial oxygen level and bicarbonate content on iron corrosion was examined during the early stages of a storage at 90 degreesC. The nature of corrosion products formed on iron surface was investigated through FTIR, Raman spectrometry and scanning electron microscopy. It has been shown that high bicarbonate content (1 M) promotes the formation of siderite whatever the initial oxygen level. Decreasing the bicarbonate content (from 0.1 to 0.001 M) will favour the formation of Fe-II(OH-)(x)(HCO3- /CO32-)(y) species with increasing x values and decreasing y values. Fe-II(OH-)(x)(HCO3-/CO32-)(y) species may suffer a series of transformations into green rust GR1(CO3) (intermediate species), Fe-II(OH-)(n)(HCO3-/CO32-)(m) gel-like precipitate, magnetite or lepidocrocite depending on the initial oxygen leveL @ 2001 Elsevier Science Ltd. All rights reserved.