Role of aqueous extract of celery (Apium graveolens L.) seeds against the corrosion of aluminium/sodium hydroxide systems

In this study, hydrogen evolution (HE) and weight loss (WL) measurements were applied to evaluate the role of an aqueous extract of celery (Apium graveolens L.) seeds (AECS), in inhibiting the corrosion of aluminium/sodium hydroxide systems. It was found that corrosion rates obtained from the measurements increase with increasing the alkali concentration giving reaction order about 0.68. The addition of increasing amounts of AECS inhibits the corrosion rate of Al in 0.25 M and maximum inhibition efficiency of 93.33% was obtained at 1.50 g L-1. While at certain concentration of inhibitor (0.50 g L-1) the inhibition efficiency increases with increasing alkali concentration up to 0.25 M, after which it started to decrease. The inhibitor mechanism was discussed on the basis of its adsorption on Al surface from 0.25 M NaOH. Langmuir and Dubinin-Radushkevich isotherms are the models that best fit the adsorption data. While FTIR spectroscopy confirmed the adsorption of inhibitor species on the Al surface. The thermodynamic parameters were determined and discussed.