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 Na-4[CuN(CH2PO3)(3)]center dot 13H(2)O 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 Na-4[CuN(CH2PO3)(3)]center dot 13H(2)O complex differs significantly from the previously studied complexes Na-4[ZnN(CH2PO3)(3)]center dot 13H(2)O and Na-4[Cd(H2O)N(CH2PO3)(3)]center dot 7H(2)O. In the potential range -0.66 horizontal ellipsis -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.