Avaliação do comportamento de heterociclos mesoiônicos solubilizados em microemulsão de óleo de côco saponificado como inibidores de corrosão

Abstract

Oil is a complex mixture of hydrocarbons containing impurities such as sulfur, oxygen, naphthenic acids, chlorides and carbon dioxide. These are largely responsible for corrosion of pipes and equipment used in exploration, production and petroleum refining. Given this situation it is necessary to invest in new technologies that act to minimize the corrosion processes. The microemulsion systems and mesoionic compounds has been the subject of great interest for application as corrosion inhibitors, because its chemical structure contributes to the formation of a layer of film on the metal surface. The structural characteristics of mesoionic potentiate this inhibition, because the presence of heteroatoms and electrons  favors the adsorption process, giving good stability of the protective film. Study evaluates the effectiveness of corrosion inhibiting compounds derived from mesoionic 1,3,4-triazolium-2-thiolate (MI-1 without replacement, MI-2 group methoxy and MI-3 group substituent nitro) solubilized in microemulsion saponified coconut oil (SCO-ME ), with the corrosive medium NaCl solution at 10,000 ppm on the carbon steel AISI 1020. Efficiency is assessed by electrochemical techniques of extrapolation of Tafel curves and electrochemical impedance. The results point to the displacement effect of the corrosion potential to anodic regions, in all cases studied, suggesting a behavior of anodic inhibitor. Systems exceed 80% efficiency in their critical concentrations and the values of ΔGads characterize the mechanism of physisorption for the mesoionic MI-1 and MI-3 and chemisorption-physisorption for MI-2. The processes of adsorption isotherms follow the Langmuir model.