Carob seed oil: an efficient inhibitor of C38 steel corrosion in hydrochloric acid

Dris Ben Hmamou,Abdelkader Zarrouk,Fatiha Fadel,Belkheir Hammouti,Rachid Salghi,Omar Benali,Hassan Zarrok

doi:10.1186/2228-5547-3-25

Abstract

Abstract Background The carob seed oil (CO) was tested as inhibitor of the corrosion of C38 steel in 1 M HCl by weight loss and electrochemical measurements. The extract was found to inhibit the corrosion of C38 steel in 1 M HCl. Results The results of the study reveal that the inhibition efficiency of CO depends on its concentration and attains approximately 86.7% at 0.5 g/L. Polarization curves reveal that CO is a mixed-type inhibitor. Changes in impedance parameters (charge transfer resistance, R t, and double-layer capacitance, C dl) were indicative of CO adsorption on the metal surface, leading to the formation of a protective film. The effect of temperature on the corrosion behavior with the addition of 0.5 g/L of carob seed oil was studied in the temperature range of 298 to 328 K. Conclusions Results show that the inhibition efficiency of the plant extract increases with increasing temperature, and the adsorption of the latter on the C38 steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution processes were also determined.

Highlights

Premature deterioration of concrete structures mainly occurs due to the ingress of chloride ions and carbon dioxide [1]
Some authors argue that those compounds which are used to protect concrete reinforcement are not effective [10] when the concrete is kept immersed in NaCl solution, whereas others report that some compounds are effective in reducing corrosion rate of steel rebar in concrete contaminated with chlorides [22, 23]
It is understandable from the polarization data that at very low concentration (50 ppm), sodium nitrite acted as a corrosion antagonist, i.e., the corrosion rate of steel rebar treated with nitrite was greater than that of the rebar immersed in concrete pore solution (CPS) without nitrite

Summary

Introduction

Premature deterioration of concrete structures mainly occurs due to the ingress of chloride ions and carbon dioxide [1]. Some authors argue that those compounds which are used to protect concrete reinforcement are not effective [10] when the concrete is kept immersed in NaCl solution, whereas others report that some compounds are effective in reducing corrosion rate of steel rebar in concrete contaminated with chlorides [22, 23]. The present investigation aims to explain the behaviour of these chemical species on steel rebar in contaminated concrete pore solution. Chemicals such as trisodium citrate (98%), sodium chloride (> 99.9%), NaNO2 (EMSURE®) and zinc acetate (> 99%) were purchased from Merck Millipore. To investigate the surface morphological changes on the steel rod dipped in simulated concrete pore solution [46, 47], microscopic studies were performed using Leica Stereo Microscope (S8ACO)

Results and discussion

NaNO2 50ppm

Conclusions