ABSTRACTImidazolines have been used in the area of corrosion inhibition since at least the mid 1940?s when it was shown that long chain organic compounds with polar functional groups had corrosion inhibition properties when applied to oil-field environments. Many fundamental studies involving imidazoline-type compounds have been conducted and reported but although many acknowledge that conventional imidazoline contains multiple species, i.e., imidazoline, amide precursor etc., none have endeavoured to separate/isolate the various components. Therefore, the extent to which each of the components in an imidazoline mixture contributes to observed properties, i.e., corrosion inhibition performance, toxicity, biodegradation and bioaccumulation are not quantitatively known.
This paper reports the synthesis, separation/isolation and performance characteristics of various imidazoline species synthesised from oleic acid (OA) and diethylenetriamine (DETA). Also reported, are initial investigations into the inhibitory performance characteristics of each of these isolated species.
INTRODUCTIONImidazolines have been used in the area of corrosion inhibition since at least the mid 1940?s when it was shown that long chain organic compounds with polar functional groups had corrosion inhibition properties when applied to oil-field environments.
The pathway to the use of imidazolines is not clear but it is probable that early workers found that certain long chain Fatty Acids (FA?s) and Amines could be used as oil field corrosion inhibitors at low concentrations. From there it would be an intuitive step to blend mixtures of these chemicals in order to obtain the most cost effective products. Such mixtures are salts and although they provide good inhibition properties they are often highly viscous liquids which are difficult to work with and formulate products from.
For a chemist the obvious answer would be to try to react these components together. Heating to moderate temperatures (~160ºC) produces an ?amide? whilst further heating to higher temperature (~230ºC) produces an ?imidazoline?. Both of these species provide corrosion inhibition properties although their manufacture adds significant cost due to the chemical facilities and energy required. Despite this the imidazolines have proved astonishingly successful commercially. This is because they are liquids at ambient conditions with relatively low viscosities. This makes them easy to formulate into products for use in a wide range of applications and climatic conditions.
Many fundamental studies involving imidazoline type compounds have been conducted and reported 1,2,3,4. Although some of these studies acknowledged that a conventional imidazoline probably contains multiple species, i.e., imidazoline, amide precursor, diamide and imidazoline amide, none have endeavoured to fully separate or isolate the various components. In efforts to further understand the ?mechanism? of inhibition afforded by conventional imidazoline mixtures, an understanding of the characteristics of each component is required.