Effect of Corrosion Inhibitor Alkyl Tail Length on the Electrochemical Process Governing CO2 Corrosion of Mild Steel

Four different model compounds were synthesized and utilized in this research to relate inhibitor alkyl tail length to changes in the activation energy of the electrochemical process associated with CO2 corrosion of an API 5L X65 steel at pH 4.0. The molecular structure of the model compounds was composed of the same head group, dimethyl-benzyl ammonium, with four different alkyl tail lengths corresponding to butyl (-C4H9), octyl (-C8H17), dodecyl (-C12H25), and hexadecyl (-C16H33). In data analysis, the chemical component of the total activation energy was calculated using an Arrhenius-type relationship and by working at the potential of zero charge (PZC). A linear relationship between the tail length of the corrosion inhibitor and the change in the activation energy of the corrosion electrochemical process was determined, suggesting that the tail modifies the activation energy of the electrochemical process underlying CO2 corrosion.