The iron carbonate corrosion product layer formed on mild steel in carbon dioxide (CO 2 ) environments is known to retard corrosion. When not fully covering the steel surface, it may also lead to initiation of localized corrosion, due to a galvanic effect. In this work, the stability of a protective iron carbonate layer has been studied at 80°C over a relatively wide range of bulk pH. Experiments were done in a glass cell using a threeelectrode system. Electrochemical techniques such as linear polarization resistance (LPR) and potentiodynamic polarization (PP) were used. Surface analysis techniques (scanning electron microscopy [SEM], x-ray diffraction [XRD], and transmission electron microscopy [TEM]) were used to confi rm the composition and structure of the protective layer. Experimental results confi rmed a pseudo-passive behavior, indicated by a positive shift in the open-circuit potential and a signifi cantly retarded corrosion rate for systems at pH 6.0 and above. However, a stable and protective pseudo-passive layer could not be formed at pH 5.6 or lower.

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A dianhydride monomer containing 4,5-diazofluorene was synthesized, and the corresponding organo-soluble polyimides exhibited good comprehensive properties.