科研之友
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摘要
Preventing corrosive action induced by the presence of chlorine in utility water used as a coolant in cooling towers is a challenging task. Anodic inhibition is one of the commonly used techniques for protecting metallic parts of the cooling towers. In this study, the effect of chloride ions on the sodium nitrite (NaNO2) inhibitor concentration was investigated for the protection of carbon steel pipes under controlled conditions of mass transfer. A rotating cylinder electrode system was utilized to provide quantified hydrodynamic mass transfer conditions. Potentiostatic polarization experiments were carried out at 313 K and rotational speeds of 0, 200, 350 and 500 rpm. It was selected a typical industrial chloride solution at a concentration of 250 ppm NaCl. The experiments were conducted in the presence of NaNO2 with different concentrations depending on the [NaNO2/NaCl] molar ratio, i.e. ratios of 0 to 1. A new calculation was used to find the best protection value which depends on the passive film stability in the polarization curve. The current analysis revealed that the new method for predicting the optimum protection value is more reliable than the conventional corrosion current density based technique.
