Avaliação da ação anticorrosiva do extrato aquoso de folhas de oliveira na proteção do aço-carbono AISI 1020 em meio de HCl 1 mol L-1

• Autor(a) principal: Sá, Priscilla Ruas Mesquita de
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/12074
• topic: Olive leaves; Corrosion inhibitor; Electrochemical assays; Weight loss measurements; Carbon steel; Acid medium; Experimental design; Folhas de oliveira; Inibidor de corrosão; Ensaios eletroquímicos; Ensaios de perda de massa; Aço-carbono; Meio ácido; Planejamento de experimentos; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA

The use of corrosion inhibitors is one of the most widely used methods to protect carbon steel parts and piping against corrosion. However, despite being efficient, many commercial corrosion inhibitors present high toxicity, causing problems for man and the environment, and with this, many studies have been carried out in order to replace them with environmentally non-aggressive products. Among these new types of inhibitors are organic compounds from plant extracts or agricultural residues, which act as good corrosion inhibitors due to the presence of heteroatoms and/or polar groups in their structure. In the present Dissertation, we evaluated the inhibitory action of aqueous extracts of olive leaves in the corrosion of 1020 carbon steel in HCl solution 1 mol L-1, employing total immersion (IT) and electrochemical assays (Electrochemical Impedance Spectroscopy - EIS, Potentiodynamic Polarization - PP and Linear Polarization Resistance - LPR). From the tests carried out, it was possible to verify that the extracts acted as good corrosion inhibitors in the studied medium. In the results obtained by EIS, the increase of the diameter of the capacitive loop was observed in the presence of inhibitory extracts, whereas the PP technique showed that these extracts acted as mixed inhibitors. These results, together with that observed by the IT assays and scanning electron microscopy (SEM), confirmed the presence of a protective film adsorbed on the surface of the carbon steel specimen, probably formed by the presence of phenolic compounds with antioxidant properties in the extracts, which would be responsible for the corrosion protection of the metal. It was verified that the components present in the extracts were physically adsorbed on the surface of the carbon steel and that this adsorption obeyed the Langmuir Isotherm. In addition, the use of an experimental design 23 with triplicate at the central point evaluated the influence of the parameters extraction time (t), extraction temperature (T) and extract concentration (C), on the charge-transfer resistance (Rtc) and corrosion rate (Wcorr) responses. From the results of the tests carried out, it was possible to verify that there is a general tendency that higher values of E.I. are obtained by using larger t and T, and a maximum value of 96.39% was reached when the extracts were added, at a concentration of 12% (v/v), obtained at 100°C for 40 minutes, to the HCl solution 1 mol L-1. The analysis of total phenolic compounds showed that this was the condition in which the highest phenol content was obtained, which corroborated the results obtained in the experimental design