Synergistic Combination Effect of Salvia officinalis and Lavandula officinalis on the Corrosion Inhibition of Low-Carbon
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TECHNICAL ARTICLE—PEER-REVIEWED
Synergistic Combination Effect of Salvia officinalis and Lavandula officinalis on the Corrosion Inhibition of Low-Carbon Steel in the Presence of SO422- and Cl2-Containing Aqueous Environment Roland Tolulope Loto . Richard Leramo . Babatunde Oyebade
Submitted: 4 July 2018 / in revised form: 15 August 2018 Ó ASM International 2018
Abstract The corrosion inhibition of low-carbon steel in 1 M H2SO4 and HCl solutions by the admixture of Salvia officinalis and Lavandula officinalis essential oil extracts was studied through potentiodynamic polarization analysis, coupon measurement and optical microscopy. The carbon steel undergoes severe surface deterioration in H2SO4, while the morphology of the steel from HCl showed selective deterioration with numerous corrosion pits in the absence of the oil extracts. The extracts performed effectively in the acid media with optimal inhibition efficiency of 86.92 and 96.90% in H2SO4, and 84.68 and 97.59% in HCl from potentiodynamic polarization and coupon analysis. The oil extract displayed anodic inhibition properties in H2SO4 due to surface coverage of the steel and cathodic inhibition in HCl due to selective precipitation of extract molecules. Thermodynamic calculations show the extracts adsorbed onto the steel surface, effectively suppressing the corrosion reactions through chemisorption mechanism according to the Langmuir, Frumkin and Freundlich adsorption isotherms. Keywords Steel
Corrosion Inhibition Essential oil
Introduction The cost of low-carbon steels (LCS) coupled with desirable mechanical and physical properties is responsible for their extensive application worldwide [1]. These types of carbon R. T. Loto (&) R. Leramo B. Oyebade Department of Mechanical Engineering, Covenant University, Ota, Ogun State, Nigeria e-mail: [email protected]
steels can be quenched and tempered for increased strength and easily formed, machined, welded and fabricated. They have a good combination of strength and ductility and may be hardened and carburized when necessary. Their application ranges from cold-headed fasteners and bolts to highvolume machine component applications, such as shafts, spindles, pins, rods and sprocket assemblies. Some find applications in the material used to produce crankshafts and couplings, etc. However, the inability of these steels to passivate in aggressive environments due to the absence of alloying elements such as Cr, Ni and Mo is a major short coming to their useful service life. Low-carbon steels have very weak resistance to corrosion which limits their application to specific environments and hence their versatility. Chemical compounds known as corrosion inhibitors have been extensively used to hinder the corrosion of carbon steels and in some cases increase the number of conditions where they can be applied. Most effective corrosion inhibitors are of inorganic origin and have been known to be expensive, toxic and dangerous to the environment. As a result, there is a need for cost-effective, economical a
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