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 Na 4 [Cd(H 2 O)N(CH 2 PO 3 ) 3 ]·7H 2 O 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/dm 3 Na 4 [Cd(H 2 O)N(CH 2 PO 3 ) 3 ]·7H 2 O at a concentration of 0.025–1.00 g/dm 3 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/dm 3 , encouraging corrosion. The minimum corrosion rate is achieved at a concentration of Na 4 [Cd(H 2 O)N(CH 2 PO 3 ) 3 ]·7H 2 O 0.15 g/dm 3 regardless of the concentration of Cl – ions. At Cl – ion concentrations of 50 mg/dm 3 and more, Na 4 [Cd(H 2 O)N(CH 2 PO 3 ) 3 ]·7H 2 O is ineffective as a corrosion inhibitor.