Effect of Corrosion Inhibitor Active Components on Corrosion Inhibition in a Sweet Environment

In sweet corrosion, corrosion scales such as iron carbonate are formed on the internal surfaces of oil and gas production and transport systems.  Depending on the type of corrosion inhibition program and the age of production system before chemical treatment is implemented, the presence of corrosion scale could affect the performance of the inhibitor.  Previous work completed by Champion Technologies investigated the interaction of iron carbonate scale and three corrosion inhibitor generic actives, namely, quaternary amine, imidazoline, and phosphate ester, and their effects on corrosion rate and corrosion scale morphology.  The first part of this study is a continuation and examines two more generic compounds: quaternary amine dimer and alkyl pyridine quaternary amine.  Experiments were performed using a three electrodes setup in glass cells.  Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS) were used to measure corrosion rates and to monitor the active-scale interaction.  Scanning Electron Microscopy (SEM) was used to observe the morphology of the iron scale layer.  

The second part of this paper explores aggregate formation for several generic inhibitor actives.  Most inhibitor actives are surfactants which form aggregates as micelles above the Critical Micelle Concentrations (CMC).  In theory, maximum inhibition should be observed around the CMC since additional surfactant molecules lead to the formation of micelles and do not contribute to corrosion inhibition.  This concept is discussed in this paper and the relationship between surfactant concentration, surfactant adsorption and corrosion inhibition is analyzed.