Coconut coir dust extract as a novel green corrosion inhibitor for carbon steel in the chloride-contaminated concrete pore solution

The potential of coconut coir dust to inhibit corrosion, especially the pitting of rebars in concrete was tapped by electrochemical techniques. Electrochemical impedance spectroscopy and linear polarization results show that both deionized water and ethanol extracts of coconut coir dust can slow down corrosion development by forming a protective film even after long-term exposure to chloride and the latter performs better and is more stable. Cyclic potentiodynamic polarization results further show that ethanol extract at a concentration of 0.1 g/L can significantly delay the initiation of pitting. This inhibitor has exhibited the highest inhibition efficiency, which can be sustained at over 90 % even after six months of immersion in solutions with high chloride concentration, but increasing the concentration of the inhibitor does not result in any additional improvement in its efficiency. Critical chloride concentration for corrosion initiation prediction and corrosion resistance evaluation was also discussed.