Corrosion Inhibition of Carbon Steel by Blends of Gluconate/Benzoate at Temperatures Up to 60°C

摘要

The inhibition of carbon steel in solutions of mixtures of calcium- and zinc-gluconate with sodiumbenzoate was investigated in the temperature range from 25° to 60°C, under atmospheric conditionsin stagnant solutions prepared with the tap water. The efficiency and the mechanism of inhibitionwere estimated by potentiodynamic polarization measurements. The influence of the concentrationand the ratio of gluconate/benzoate on the anodic reaction and an observed cathodic effect, indicatingslowing down the oxygen reduction process, relevant to the concentration of zinc ions, have beendemonstrated.The performed inhibition of carbon steel, as shown by polarization data, may be attributed to theadsorption of gluconate along with benzoate or/and to the formation of a low soluble iron gluconatecomplex on the metal surface. The inhibition is enhanced by the cathodic polarization mechanismresulting in the precipitation of a zinc hydroxide film, due to the local cathodic gradient of hydroxylions. Gluconates act also as sequestring agents preventing a deposition of calcium carbonate fromhard waters.Results obtained by electrochemical measurements were confirmed by immersion tests, and could beof interest for the application in cooling water treatement systems, and for the injection water in oiland gas recovery.Investigated compounds are environmentally acceptable being non-toxic and non-polluting.