Purpose - To develop a new corrosion inhibitor formulation for carbon steel in low chloride environments.
Designlmethodology/approach - Corrosion inhibition efficiencies were evaluated by the weight loss method and by impedance measurement
studies. The nature of the inhibition process was evaluated using potentiostatic polarization studies. The nature of the protective film was investigated
using X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The concept of synergistic effect was used in the
development of the new synergistic inhibitor formulation.
Findings - A new corrosion inhibitor formulation, containing tertiary butyl phosphonate (TBP), zinc ions and citrate, has been developed to control the
corrosion of carbon steel in low chloride environments. This inhibitor formulation was found to offer a maximum inhibition efficiency of 96 per cent in a
neutral pH test environment. It was interesting to observe that the binary system, consisting of higher concentrations of the TBP and zinc ions, offered
only 79 per cent inhibition efficiency. The ternary system, consisting of relatively lower concentrations of the phosphonate, zinc ions and citrate offered
a higher (96 per cent) efficiency. This ternary inhibitor system also was found to be efficient in acidic as well as basic environments in the pH range 5-8.
The inhibitor combination was determined to function as a "mixed8'-type inhibitor, though being predominantly cathodic. A plausible explanation of the
mechanism of corrosion inhibition is proposed.
Practical implications - The ternary inhibitor formulations based on phosphonate, zinc ions and another environmentally friendly synergists like
citrate will be quite useful for corrosion inhibition of carbon steel in cooling water systems as they contain relatively less concentrations of phosphonate
and zinc ions.
Originalitylvalue - The research paper presents the results of a new synergistic inhibitor formulation and also discusses the mechanistic aspects of
corrosion inhibition