2014 International Conference on Energy, Environment and Materials Engineering (EEME 2014) ISBN: 978-1-60595-166-9 Electrochemical Behavior of API x70 Steel Plates in Two Protic Ionic Liquids Maria Rita ORTEGA VEGA 1,a,* , Sandra Raquel KUNST 1,b , Tiago Lemos MENEZES 2,c , Silvana MATTEDI 3,d , Miguel IGLESIAS 3,e and Célia de Fraga MALFATTI 1,f 1 Universidade Federal do Rio Grande do Sul. Av. Bento Gonçalves, no 9500, Bloco 4, Prédio 75, 2o Andar, Porto Alegre – RS, Brazil 2 Faculdade da Serra Gaúcha – FSG, Faculdade de Design, Rua Os Dezoito do Forte, 2366, Caxias do Sul – RS, Brazil 3 Universidade Federal da Bahia. R. Aristides Novis 2 - 2o. Andar Federação. Salvador – BA, Brazil a mortegavega811@gmail.com, b tessaro.sandra@gmail.com, c tiagolm@gmail.com, d silvana@ufba.br, e miguel.iglesias@ufba.br, f célia.malfatti@ufrgs.br *Corresponding author Keywords: Protic Ionic liquids, API X70 steel, EIS. Abstract. A corrosion study of two different protic ionic liquids on API X70 steel was conducted. Each protic ionic liquid is composed by an amine anion and a carboxylic cation. Carboxylic cation length was varied in order to evaluate the influence of this factor in the corrosion behavior when the protic ionic liquid is in contact with the API X70 steel substrate. Morphological characterization was carried out by SEM and electrochemical behavior was evaluated by electrochemical impedance spectroscopy and open circuit potential (OCP) monitoring. Results showed that the longer the PIL anion chain the less the corrosion brought about to the substrate; also, 2HEABu, the PIL with the longer anion chain showed corrosion inhibitor properties. Introduction The field of ionic liquids (ILs) is growing at a very fast rate, as the many beneficial properties of these liquids are identified and utilized. A subset of ILs are protic ionic liquids (PILs), which are easily produced through the combination of a Brønsted acid and Brønsted base [1]. They have emerged as possible ‘‘green’’ solvents because they have very low vapor pressure and are stable within a wide temperature range and therefore have no polluting gas emissions [2]. By variation of the anion or the alkyl chain of the cation, a wide range of properties such as hydrophobicity, viscosity, density, and solvation power can be modulated, opening the possibility of tailored ILs designed for specific industrial applications [3]. Anyway, PILs application is constrained by the corrosion effects that these substances can bring about to the materials of equipment. A former study was conducted regarding an AISI 1004 steel substrate in contact with two-carbon, three-carbon and five-carbon anion chain length PILs, showing low corrosion trend [4]. API X70 was chosen as substrate in order to carry out a corrosion study varying the anion chain length for each PIL, taking into account the use of that substrate in the oil and gas industry. API X70 plates was put in contact with an aqueous PIL electrolyte and electrochemical impedance spectroscopy (EIS) tests were conducted, in order to evaluate the electrochemical behavior trend. Scanning Electron Microscopy (SEM) images were used to study the surface morphology.