Abstract
The corrosion inhibition of substituted pyridine derivatives and quaternized pyridines in the presence and absence of acetylenic alcohol synergists is reported. Electrochemical Frequency Modulation (EFM) was used as a method of monitoring corrosion rates of steel in acidic environments. Early stage pitting was evaluated via scanning electron microscope (SEM) for comparison of measured corrosion rates to observed pit formation. EFM was found to be a reliable and accurate method of monitoring general corrosion rates over time, and causality factor data was found to depend heavily on the type of corrosion occurring at the metal surface. In addition, the pyridine derivatives were found to have complex substituent effects on corrosion inhibition, with unsaturated substituents most significantly enhancing the performance relative to pyridine. Nearly all of the benzyl quaternized pyridine derivatives performed similarly to non-quaternized derivatives in the acid media, suggesting similar mechanisms of action, except for the N-benzyl quinolinium quaternary amine, which displayed significantly enhanced behavior relative to the amine. The alkynol synergists gave similar efficacies under the test conditions regardless of chain length or conformation. Substituent effects on the pyridine ring showed varying interactions with alkynols in pyridine-alkynol blends, with both synergistic and antagonistic effects being observed.
Introduction
Acid stimulation has been used to increase the permeability of rock formations for oil, gas and water wells dating back as far as the 19th century. Injection of acids into the formation selectively dissolves certain minerals allowing fluids to flow upwards into the well. Hydrochloric acid, hydrofluoric acid, and less active organic acids can be selectively used to dissolve carbonate minerals, sandstones, and some types of formation damage. This can be done using either fracturing or matrix acidizing techniques. There are many nuances and possible complications to the acidizing process and corrosion of equipment is a common problem for obvious reasons.
