The Influence of the Cadmium Complex of Nitrilo-Tris-Methylenephosphonic Acid and Electrochemical Behavior of Low-Carbon Steel in Neutral Aqueous Media Containing Chloride Ions.

The potentiodynamic method was used to study the influence of the cadmium complex of nitrilo-tris-methylenephosphonic acid Na₄[Cd(H₂O)N(CH₂PO₃)₃]·7H₂O on the corrosion-electrochemical behavior of low-carbon steel in neutral aqueous media in the presence of Cl ions^-. The composition and structure of passive films formed at different potentials and composition of the medium were studied by X-ray photoelectron spectroscopy with layer-by-layer etching. When the content of Cl^– ions up to 20 mg/dm³ Na₄[Cd(H₂O)N(CH₂PO₃)₃]·7H₂O at a concentration of 0.025–1.00 g/dm³ acts as a corrosion inhibitor, reducing the current density of anodic dissolution of the metal, and, at a concentration of more than 1.00 g/dm³, encouraging corrosion. The minimum corrosion rate is achieved at a concentration of Na₄[Cd(H₂O)N(CH₂PO₃)₃]·7H₂O 0.15 g/dm³ regardless of the concentration of Cl^– ions. At Cl^– ion concentrations of 50 mg/dm³ and more, Na₄[Cd(H₂O)N(CH₂PO₃)₃]·7H₂O is ineffective as a corrosion inhibitor. [ABSTRACT FROM AUTHOR]