Corrosion protection of a carbon steel in nuclear power plant secondary circuit conditions by film-forming amines: an impedance study

摘要

During layup periods of pressurized water reactors (PWRs), corrosion phenomena can affectmetallic components of the secondary circuit, mainly carbon steel. The use of corrosion inhibitorssuch as film-forming amines (FFA) is an interesting way to attenuate or stop these phenomena andextend the lifetime of the materials. FFA have both a hydrophilic head which can adsorb on metalsor oxides films and a hydrophobic tail which can organize rather perpendicularly to the surface andcreate a protective barrier between the metal and the oxidizing species.The aim of the present work was to investigate the effectiveness of octadecylamine (ODA) for thecarbon steels protection under various physical and chemical conditions, representative of thePWR secondary circuits. Carbon steel plates were submitted to different treatments attemperatures between 120 °C and 275 °C in an autoclave with or without ODA. The adsorption ofthe FFA on the carbon steel surface was characterized at room temperature by contact anglemeasurements and scanning electron microscopy (SEM). Electrochemical impedancemeasurements were performed in a Na_2SO_4 10~(-3) M solution to characterize both the corrosioninhibition efficiency of the ODA and to follow the film behaviour with immersion time. From theimpedance data analysis [1], the films thicknesses were extracted and were about 15-20 nm,regardless of the different treatments.