Microemulsions based on vegetable oil extracts as corrosion inhibitors: A structural study by SAXS

HENRIQUE B. GONÇALVES; CRISTIÁN HUCK IRIART; EMMANUEL V. COSTA; VICTOR H. V. SARMENTO

Rio de Janeiro

Congreso; XIV Brazil MRS Meeting; 2015

Brazilian Materials Research Society

Microemulsions (ME) are clear, stable and isotropic mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. ME are a class of micro heterogeneous systems having unique features of stability, solubilization capacity, structural morphology, physical property and applicability. They have found numerous applications in different fields such as corrosion inhibitors [1]. Advantages associated with their thermodynamic stability, optical clarity and ease of preparation enable corrosive agents to be solubilized, surfactants to be adsorbed onmetal surface and hence the corrosion is reduced. Depending on the types of oil and surfactant and environmental conditions, microemulsioned systems of varied categories, consistence and internal structures may result. This study aims to obtain microemulsioned systems using vegetable inhibitors based on A. muricata L. (Am) and A. squamosa L. (As) extracts, (Annonaceae) as oil phases (OP). Tween 80 and ethanol were used, respectively, as surfactant and cosurfactant and saline NaCl 3.5% (corrosive environment) as aqueous phase (AP). ME were analyzed by rheological measurements, where results showed a newtonian behavior and by SAXS, where the curves display and broad peak typical of ME systems with a maximum at approximately q = 1nm-1 irrespective of FO. Quantitative structural information was obtained from the ellipsoidal "core-shell" model. The adjustment of the model provided information about the maximum radius (Rmax) and minimum (Rmin) and therefore the size of the ME. ME based on Am and 96% AP presented higher size of OP.[1] A. O. Wanderley Neto, E. F. Moura, H. S. Júnior, T. N. C. Dantas, A. A. Dantas Neto, A. Gurgel, Colloids and Surfaces A: Physicochem. Eng. Aspects 398, 76? 83(2012)