Corrosion inhibition of mild steel by imidazolines and their precursors in a carbon dioxide (CO2)-containing environment was studied using rotating cylinder electrode (RCE) and linear polarization resistance (LPR) techniques. Corrosion rate-time/concentrations profiles and minimum effective concentrations obtained for a series of imidazolines and amides were evaluated in terms of the respective contributions of their constituent parts (imidazoline ring, amide/amine group, and hydrocarbon chain) to overall corrosion inhibition. Formation of inhibitor film was studied in terms of the bilayer/multilayer film model. Corrosion inhibition of various straight chain imidazolines and amides in the RCE screening test was dependent upon the type of treatment used: constant concentration or variable concentration treatment. Significant differences in activity between those inhibitors (C20 >> C12) were obtained in the continuous treatment, while no differences were observed in the variable concentration treatment. The effect of the hydrocarbon chain length of imidazolines on their corrosion inhibition was quite significant. A linear relationship was obtained between the MEC (minimum effective concentration) and hydrocarbon chain length (MEC12>MEC16>MEC18>MEC20). With the hydrophobic chain length <12, no corrosion inhibition was observed. The pronounced effect of the hydrophobic group on corrosion inhibition of imidazolines could be related to their high admicelles bilayer cohesive energies. For a specific chain length, the effect of the hydrophilic head group of nitrogen-based surfactants (imidazoline, amide, amine) was somewhat less pronounced than that of the hydrophobic group (C12 vs C18) but nevertheless significant. The results helped to illustrate the importance of the hydrophilic head group in the formation of bilayer film. Preliminary results suggest the hydrolysis of saturated, straight chain imidazolines played an important role in their inhibition. Thus, under the test conditions, stearic imidazoline hydrolyzed fairly rapidly to a product equivalent in performance to stearic amide.
Inhibition of carbon dioxide corrosion of mild steel by imidazolines and their precursors
Inhibition der Kohlendioxidkorrosion von unlegiertem Stahl durch Imidazoline und ihre Derivate
Corrosion, Houston ; 55 , 5 ; 449-455
1999
7 Seiten, 10 Bilder, 1 Tabelle, 22 Quellen
Article (Journal)
English
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