Electrochemical Behavior of an Amorphous Alloy in an Ionic Liquid and in Aqueous Media
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Electrochemical Behavior of an Amorphous Alloy in an Ionic Liquid and in Aqueous Media O. K. Lebedevaa,*, D. Yu. Kultina, A. N. Zakharova,b, and L. M. Kustova,c a Department
of Chemistry, Moscow State University, Moscow, 119991 Russia Moscow State Technical University, Moscow, 105005 Russia c Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] bBauman
Received January 23, 2020; revised January 23, 2020; accepted February 11, 2020
Abstract—A study is performed of the effect pretreatment with solutions of benzoic acid in an organic solvent has on the result from the electrochemical oxidation of amorphous alloy Fe70Cr15B15 in an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. It is established that the nature and properties of surface oxide films affect the result from the electrochemical oxidation of the alloy in an ionic liquid. Partial removal of oxide films by a solution of benzoic acid and subsequent electrooxidation in an ionic liquid reveals a nanocellular structure on the electrode’s surface. It is shown that preliminarily treating the alloy with a saturated solution of benzoic acid in acetone results in a considerable anodic shift in the corrosion potential and the formation of a more effective protective coating. Keywords: amorphous alloy Fe70Cr15B15, etching, benzoic acid, electrooxidation, ionic liquid, nanostructures DOI: 10.1134/S0036024420110205
INTRODUCTION Amorphous multicomponent alloys based on iron attract growing attention due to their high resistance to electrochemical pitting corrosion [1]. Protective oxide films on the surfaces of alloys doped with chromium additives are not always enriched with an alloying component and often correspond in composition to the ratio of components in an alloy [2]. The presence in the alloy of the third component of a non-metallic nature (e.g., Si or B) usually enhances the corrosoin stability of steels as well [3], but can lead to destruction of the crystal structure and amorphization of the solid phase. Amorphous alloy steels are of particular interest as materials that are compatible with biological tissues [4, 5], for which one requirement is resistance to different types of corrosion. The aim of this work was to study the electrochemical behavior of amorphous alloy Fe70Cr15B15 during its anodization in an ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4], along with its anticorrosion properties in relation to an aquatic environment simulating the composition of physiological saline. Due to their properties, ILs satisfy all the requirements of green chemistry. The wide window of electrochemical stability makes them particularly attractive as electrolytes. ILs based on tetrafluoroborate anions are hydrophobic and quite stable, since they do
not undergo hydrolysis, which is accompanied by the formation of fluorine-containing HPO2F2, H2PO3F, H3PO4, and HF products [6]. EXPERIMENTAL Amorphous alloy Fe70Cr15B15 was prepared from
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