Iron carbonate (FeCO3) is a carbon dioxide (CO2) corrosion by-product known to provide corrosion resistance to carbon steel in specific environmental conditions. Nonetheless, it suffers from both chemical dissolution and mechanical damage when the pH is low and when subjected to particle impingement, respectively. This work aims at understanding whether incorporating two amino acids, mainly cysteine and glycine help improve either the reduction in corrosion rate or the mechanical properties of FeCO3. In addition to their corrosion inhibition properties, it is anticipated that incorporating such organic moieties directly into the FeCO3 layer as it grows should have a positive effect on properties such as the modulus, in turn making the layer less prone to internal stresses and disbandment. Our results show that both amino acids incorporate within the FeCO3 matrix and affect the hardness and modulus of the hybrid layer. Moreover, cysteine is able to reduce localized corrosion attack in such environments.


Oil and gas production in a CO2 saturated environment is known to lead to corrosion due to dissolved carbonic acid. However, when the conditions are favorable, a protective FeCO3 layer can also form which reduces the material degradation of the underlying steel by up to ten or a hundred times.1 The formation of FeCO3 is possible via the reaction shown in equation 1.


FeCO3 can be removed as a result of many detrimental effects such as chemical dissolution due to pH fluctuations (especially when the acidity increases) but also from internal stresses that lead to its cohesive disbandment and erosion attack due to silica sand particles.2 Once partially damaged, the beneficial material mitigation effect offered by FeCO3 will on the contrary lead to a higher risk of localized corrosion attack.

Engineering a more resilient FeCO3 has been successfully carried out in our laboratories and a hybrid organic-inorganic FeCO3 has shown improved electrochemical and mechanical properties.3 Many researchers have studied the effect of amino acids on various engineering materials including mild steel, which is one of the main materials of choice in oil and gas sector.4

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