This work has been carried out to investigate the effect of iron carbonate films formed on API-5L X65(1) pipeline steel on the material degradation mechanisms in erosion-corrosion. The experimental procedure includes a precorrosion process to form four types of corrosion films in different conditions: (i) transparent, (ii) cementite, (iii) iron carbonate, and (iv) iron carbonate/cementite. The erosion-corrosion experiments were conducted using a recirculating impinging jet apparatus. In-situ corrosion rate values were monitored at a flow velocity of 7m/s, 50°C with addition of 100 mg/l sand in Forties brine saturated with CO2. The effects of the pre-formed films and the mechanisms relating to corrosion and erosion-corrosion processes have been identified and analysed using surface analysis techniques (SEM, AFM) and nano-indentation. It has been found that the erosion-corrosion conditions in this study severely damage the pre-formed corrosion films and hinder the re-formation of the protective films. The implications of this for successful use of X65 pipeline steel in high impact energy, sand-containing fluids are discussed.

Subject
Films, Coating removal, Steel surfaces, Sand, Corrosion rate, Iron carbonate, Iron carbonate films, Protective films, Flow velocity, Iron, Precorrosion, Film formation, Erosion corrosion
Keywords:
Iron carbonate film, erosion, surface analysis, jet impingement
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2013
Association for Materials Protection and Performance (AMPP)
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