Formulations of hybrid-type corrosion inhibitors for carbon steel in desalination water plants

Desalinated potable water is corrosive to carbon steel due to the lack of natural ionic equilibrium following to-demineralization process by reverse osmosis (desalination). In this work, the inhibition performance of different inorganic (seven) and organic (four) inhibitors were evaluated using weight loss technique. Subsequently, a formulation composed of zinc sulfate (inorganic) and calcium gluconate (eco-friendly organic) was prepared by ratio of 15% and 85%, respectively, as a hybrid-type corrosion inhibitor for desalinated potable water on carbon steel coupons. Inhibition performance has been assessed by using weight loss (WL), open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques at 25 °C throughout a wide concentration range from 5 up to 1000 ppm. The findings revealed that the inhibition performance was improved by more than 90% compared to the blank sample due to the synergistic action of the inhibitor. Also, there is a significant agreement between weight loss, EIS, and PDP techniques. Furthermore, the mechanism of inhibition action was also discussed, which revealed that the prepared blend is acting as both anodic and cathodic inhibitor pathways simultaneously and synergistically.