Having a better understanding of the effect of increased temperature on the performance of organic corrosion inhibitors (CIs) is beneficial for their usage in high temperature environments. The present work focuses on studying the effect of temperature on inhibition behaviours of an in-house synthesized CI model compound, tetradecyl phosphate ester (PE-C14), in a simulated refinery environment. Surface saturation concentrations at three temperatures (25°C, 55°C, and 80°C) are determined by exploiting corrosion rate evolution. At low temperature (25°C), a gelatinous film formed on the rotating cylinder electrode (RCE) surface that significantly affected the limiting current, although the PE-C14 layer was poorly adherent. At elevated temperatures (55°C and 80°C), a thick, adherent and readily detectable by EDS and Raman spectroscopy, PE-C14 layer formed on the RCE surface to achieve much lower corrosion rate (inhibition efficiency close to 100%) with relatable surface saturation concentrations.
Organic corrosion inhibitors (CIs) are widely employed in the oil and gas industry to protect carbon steel pipelines against internal corrosion. The high inhibition efficiency of organic CIs at extremely low concentration can be attributed to their amphiphilic molecular structures. This structure enables the formation of self-assembled films that act against corrosion via the adsorption of their hydrophilic head group on the steel substrate and the repellence of aqueous corrosive species by their hydrophobic tail. Consequently, any factors affecting the film formation of organic CIs could lead to changes in inhibition behaviors.
The use of organic CIs in high-temperature environments, i.e., up to 80°C here, has particular challenges: not only uninhibited corrosion rates (CRs) are largely accelerated, but also inhibition performance could be affected dramatically. The high temperature could affect the organic CIs inhibition performance from different aspects, such as influencing the adsorption process,1–5 inducing chemical degradation,6, 7 enabling polymerization,8, 9 etc. Even through the performances of organic CIs at elevated temperatures have been extensively studied,1–9 the mechanisms behind these effects require further elucidation. Moreover, the effects of temperature on inhibition are often different from inhibitor to inhibitor. Consequently, more research work about the effect of high temperature on organic CIs will be beneficial for their optimal usage.
