Impact of the Chelate Complex of Nitrilotris(methylenephosphonic Acid) with Copper on the Corrosion-Electrochemical Behavior of Carbon Steel in an Aqueous Medium.

The effect of the Na4[CuN(CH2PO3)3]·13H2O complex compound with a chelate structure on the corrosion-electrochemical behavior of 20# steel in a borate buffer solution at pH 7.4 and natural aeration was studied using the potentiodynamic method and methods of X-ray photoelectron spectroscopy and surface scanning electron microscopy with microanalysis. It was established that in the concentration range of 0.2–1.0 mM the complex under study inhibits the anodic dissolution of the metal and drives it at higher concentrations. In terms of its effect on the corrosion-electrochemical behavior of steel, the Na4[CuN(CH2PO3)3]·13H2O complex differs significantly from the previously studied complexes Na4[ZnN(CH2PO3)3]·13H2O and Na4[Cd(H2O)N(CH2PO3)3]·7H2O. In the potential range –0.66...–0.05 V relative to the Ag,AgCl|KCl-electrode (SSCE) a layer of metallic copper is generated on the surface in the form of nano-sized crystals, shielding the surface of the steel. In the potential range of 0.05–0.13 V (SSCE), metallic copper is oxidized, and with a further increase in the potential, a layer of mixed iron and copper oxides is formed. [ABSTRACT FROM AUTHOR]