Mixed Copper-Nickel Nitrilo- tris -Methylenephosphonic Acid Complexes: Synthesis, Structure, and Effect on the Corrosion
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d Copper-Nickel Nitrilo-tris-Methylenephosphonic Acid Complexes: Synthesis, Structure, and Effect on the Corrosion-Electrochemical Behavior of Carbon Steel F. F. Chausova, *, N. V. Lomovaa, N. V. Somovb, S. M. Reshetnikova, V. L. Vorob’yova, and I. S. Kazantsevaa aUdmurt
Federal Research Center, Ural Branch, Russian Academy of Sciences, Izhevsk, 426067 Russia b Lobachevsky State University, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received March 19, 2020; revised April 10, 2020; accepted May 27, 2020
Abstract—The synthesis and crystal properties of mixed nitrilo-tris-methylenephosphonic complexes [CuxNi(1−x){N(CH2PO3)3}]Na4 · nH2O (x = 0–1) are studied. The interaction between the obtained complexes and surfaces of steel 20 is studied via XPS. The effect of adsorbed complex layers have on the corrosion and electrochemical behavior of the steel surfaces in an aqueous medium is studied by potentiodynamically method. It is shown that the interaction between copper-nickel complexes and a steel surface is accompanied by exchange processes and results in the formation of surface layers of varying composition and anticorrosion properties. DOI: 10.3103/S1062873820090117
INTRODUCTION Much attention is being given to studying complexes of nitrilo-tris-methylenephosphonic acid H6{N(CH2PO3)3} (H6NTP) with metals [1, 2]. NTPmetal complexes are used as inhibitors of steel corrosion in aqueous media [3, 4]. NTP complexes with copper [5] and nickel [6] have been examined in detail, but mixed copper-nickel complexes remain unstudied. This work describes the synthesis and structural features of copper–nickel NTP complexes [CuxNi(1 – x){N(CH2PO3)3}]Na4 · nH2O (x = 0–1) and their effect on the corrosion and electrochemical behavior of steel in aqueous media. EXPERIMENTAL Mixed complexes were synthesized by dissolving weighed portions of hydroxycarbonates in an aqueous solution containing 1 mol of NTP (twice recrystallized, not more than 0.3% PO3– 4 ) and 4 mol of NaOH (chemically pure, GOST 4328-77). Crystals of the mixed complexes were obtained from the solution at room temperature via slow evaporation of the solvent. X-ray diffraction analysis was performed on Kappa single Xcalibur and Oxford Diffraction Sapphire3 Gemini S diffractometers from Rigaku XtaLAB Pro. Primary fragments of the structures were found directly. Atomic positions were determined from differ-
ence electron density synthesis and refined in the anisotropic (for hydrogen atoms in the isotropic) approximation using the least squares approach on |F|2. The atomic fractions of copper and nickel in the obtained crystals were determined in three ways simultaneously: via X-ray fluorescence (on an Innov-X Alpha-2000 spectrometer, United States), spectrophotometry (reagent-free spectrophotometry of [Cu(H2O)6]2+ and [Ni(H2O)6]2+ complexes using an SF-56 spectrophotometer), and titration (according to GOST 10398-76 for the titration of nickel after the deposition of copper with sodium dithionite Na2S2O4, and differential determination of copper). X-ray phase a
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