Development of a structure-activity relationship for oil field corrosion inhibitors

Corrosion rare data for mild steel corrosion inhibitors in carbonated brine media were fitted to the Temkin adsorption isotherm. The fundamental constants of the Temkin adsorption isotherm, i.e., molecular interaction and adsorption equilibrium constants, were used to glean important information about the behavior of adsorbed corrosion inhibitors. Adsorption data were also used to calculate Delta(ad)H, Delta(ad)G, and Delta(ad)S, and the results demonstrated that some compounds are chemisorbed onto the electrode. Significantly, it has been found that chemisorption of corrosion inhibitors can yield very good film persistency (i.e., corrosion protection even when the inhibitor is no longer present). Molecular modeling using the quantum mechanical program PCSpartan plus, along with a comparative analysis of adsorption data for a broad range of inhibitor molecules, has been used to derive a tentative structure/activity relationship for some oil field corrosion inhibitors. (C) 1999 The Electrochemical Society. S0013-4651(98)07-066-9. All rights reserved.