Pineapple stem extract (Bromelain) as an environmental friendly novel corrosion inhibitor for low carbon steel in 1 M HCl

Abstract

The anticorrosion behavior of bromelain on low carbon steel (LCS) in 1 M HCl solution was studied employing weight loss, potentiodynamic polarization measurement (PDP), electrochemical impedance spectroscopy (EIS), UV–visible spectrophotometry, and surface assessment techniques like scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) at 308–338 K. The obtained results suggest that bromelain is an excellent corrosion inhibitor and its inhibition efficiency (%η) is both concentration and temperature dependent. %η is observed to increase with an increase in bromelain concentration and an increase in electrolyte temperature. The maximum %η of 97.6% is observed at bromelain concentration of 1000 ppm at 338 K. The inhibitor adsorption on the LCS surface is in accordance with the Langmuir adsorption isotherm. As evidenced by PDP measurements, bromelain behaves as a mixed-type inhibitor and controls both anodic and cathodic processes. Adsorption free energy of the bromelain on LCS surface together with an increase in %η with the rise in temperature is suggestive of chemical adsorption. SEM micrographs show a smoother surface for inhibited LCS specimen. Analysis of variance statistically compare the difference existing between inhibition efficiencies from gravimetric, PDP and EIS technique and suggests that they are not significantly different.