Galvanic effects induced by siderite and cementite surface layers on carbon steel in aqueous CO2 environments

Joshua Owen (1) , Francois Ropital (2, 3) , Gaurav R. Joshi (2) , Jean Kittel (2) , Richard Barker (1)

1 University of Leeds
2 IFPEN - IFP Energies nouvelles
3 MATEIS - Matériaux, ingénierie et science [Villeurbanne]

Siderite (FeCO 3) and cementite (Fe 3 C) layers develop naturally on carbon steel surfaces in aqueous carbon dioxide (CO 2) environments. This study evaluates galvanic corrosion induced by such layers when coupled to bare carbon steel. In CO 2-saturated, 50 • C, pH 5 conditions, the Fe 3 C-filmed carbon steel acted as the net cathode, significantly enhancing bare steel corrosion rates. Galvanic currents induced by the FeCO 3-filmed steel were much lower, with FeCO 3 removed from the surface as Fe 3 C was revealed concomitantly on bare steel. It is proposed that the presence of Fe 3 C amongst the FeCO 3 layer is responsible for galvanic interaction, rather than FeCO 3 itself.

Mots clés: Carbon steel; Iron carbide; Iron carbonate; Galvanic corrosion; Localised corrosion; Electrochemistry

Domaines: Chimie théorique et/ou physique

Joshua Owen, Francois Ropital, Gaurav R. Joshi, Jean Kittel, Richard Barker. Galvanic effects induced by siderite and cementite surface layers on carbon steel in aqueous CO2 environments. Corrosion Science, 2022, 209 (110762), ⟨10.1016/j.corsci.2022.110762⟩. ⟨hal-03909974⟩