Microemulsions for application as corrosion inhibition: a SAXS approach

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

Campinas

Congreso; 25th Annual User Meeting LNLS/CNPEM (RAU); 2015

Laboratorio Nacional Luz Sincrotron

Microemulsions (ME) are clear, stable and isotropic mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. Microemulsions are a class of microheterogeneous systems having unique features of stability, solubilization capacity, structural morphology, physical property and applicability. They have found numerous applications in different fields from drug delivery vehicles up to corrosion inhibitors [1,2,3]. In the latter, microemulsions have generated considerable interest over the years. Advantages associated with their thermodynamic stability, optical clarity and ease of preparation enable corrosive agents to be solubilized, surfactants to be adsorbed on metal 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 (FO). Tween80 and ethanol were used, respectively, as surfactant and cosurfactant and saline NaCl 3.5% (corrosive environment) and aqueous phase (AP). The formation of ME were analyzed and verified by SAXS and rheology allowing such systems are promising corrosion inhibitors. The results shows a broad peak typical of microemulsion systems with a maximum at approximately q = 1nm-1 for all samples. 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 (R min) and therefore the size of the ME. [1] M. J. Lawrence, G. D. Rees, Advanced Drug Delivery Reviews 64, 175?193(2012) [2] R. Shlomovitz, L. Maibaum, M. Schick,Biophysical Journal 106, 1979-1985 (2014) [3] 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)