Mechanism of enhancing corrosion inhibition of carbon steel by nitrilo-tris(methylenephosphonato)zinc in neutral chloride-containing environments: electrochemical and XPS studies

The formation and structure of passive films on steel in a borate buffer environment pH= 7.4 containing Chloride ions have been thoroughly investigated. The effect of the inhibitor Na-4[ZnNTP]center dot 13H(2)O with a certain molecular structure have been studied, including the mechanism of its action. The lowest anodic dissolution current is reached at the ZnNTP concentration of about 0.6 g/L. At the initial stage of its formation, the passive film is composed of iron oxides, which may further approach the structure of magnetite. Under conditions of counter-diffusion of ZnNTP and Fe2+ ions, the heteropolynuclear complex Zn1/2Fe1/2(H2O)3 mu-H4NTP](n) is formed. As for the character of the formed chemical bonds, steel passivation in the presence of ZnNTP differs significantly from both oxide and salt passivation, and thus should be considered as a specific case, called by coordination passivation.

Automated summary

The formation and structure of passive films on steel in a borate buffer environment pH= 7.4 containing Chloride ions have been thoroughly investigated. The effect of the inhibitor Na-4[ZnNTP]center dot 13H(2)O with a certain molecular structure have been studied, including the mechanism of its action. The lowest anodic dissolution current is reached at the ZnNTP concentration of about 0.6 g/L. At the initial stage of its formation, the passive film is composed of iron oxides, which may further approach the structure of magnetite. Under conditions of counter-diffusion of ZnNTP and Fe2+ ions, the heteropolynuclear complex Zn1/2Fe1/2(H2O)3 mu-H4NTP](n) is formed. As for the character of the formed chemical bonds, steel passivation in the presence of ZnNTP differs significantly from both oxide and salt passivation, and thus should be considered as a specific case, called by coordination passivation.