Encapsulation of butylimidazole in smectite and slow release for enhanced copper corrosion inhibition

Abstract Butylimidazole (Bim) a well-known copper corrosion inhibitor was encapsulated in its cationic form, in a smectite type clay mineral (Sabga clay mineral (Sg)) by cation exchange of sodium cations located in the interlayer space of the layered clay mineral. Physicochemical characterization (XRD, FT-IR and TGA) revealed that Bim was intercalated (0.48 mmol per gram of hybrid material) in its cationic form. The intercalation was followed by an increase of the layer to layer distance from 11.4 A to 13.9 A. The composite material (Sg-Bim) was then applied as copper corrosion inhibitor in concentrated sodium sulphate solution (0.1 M) and experiments monitored electrochemically. For a given concentration of Sg-Bim, the corrosion potential increased as a function of time. The corrosion inhibition percentages obtained both by corrosion current densities (up to 80.7%) and charge transfer resistance (up to 87.0%) were found to increase with the release time. This confirmed that the clay mineral Sg effectively served as a nanocontainer for the encapsulation of Bim. Moreover, the release of Bim occurred gradually when the organoclay was immersed in concentrated saline solution. Investigations on the effect of temperature on the process confirmed that the action of released Bim against copper corrosion consisted in improving the stability of the Cu2O protecting layer, according to a physisorption mechanism.