Corrosion inhibition studies of the combined admixture of 1, 3-diphenyl-2-thiourea and 4-hydroxy-3-methoxybenzaldehyde on mild steel in dilute acid media

Roland Loto

doi:10.15446/rev.colomb.quim.v46n1.59578

Abstract

La corrosión de acero dulce es responsable de pérdidas económicas e industriales debido a su deterioro acelerado. Los derivados sintetizados de tiourea y aldehídos fenólicos con heteroátomos inhiben la corrosión por adsorción sobre el acero mediante la formación de enlaces fuertes. Por tanto, se estudiaron las propiedades de inhibición de la corrosión electroquímica de la mezcla combinada de 1,3-difenil-2-tiourea y 4-hidroxi-3-metoxibenzaldehído sobre acero dulce en medios de H2SO4 y HCl 1 M mediante análisis de pérdida de peso, método de polarización potenciodinámica, microscopía óptica y espectroscopia IR. Los resultados mostraron que la mezcla inhibe eficazmente la corrosión del acero dulce en ambas soluciones con una eficacia de inhibición óptima de 97,4% y 97,47% en H2SO4, mientras que los valorescorrespondientes al HCl son 94,71% y 89,73%. Los cálculos termodinámicos demostraron que el compuesto quimiosorbido sobre la superficie de acero bloquea la difusión de aniones corrosivos. Las imágenes micro-analíticas confirmaron la efectiva propiedad de inhibición del compuesto y su presencia en la topografía superficial del acero. Los espectros infrarrojos revelaron la presencia de los grupos funcionales del compuesto orgánico responsable de la inhibición de la corrosión. La adsorción del compuesto se dedujo siguiendo las isotermas de adsorción de Langmuir, Frumkin y Freundlich.

Highlights

Mild steel was purchased from the Steel WorksB OwodeB Nigeria and analyzed at the Materials Characterization LaboratoryB Department of Mechanical EngineeringB CovenantA This mild steel gave an average nominal composition of nominal per cent Dw/w 3P compositionB shown in Table 2A The steel had a cylindrical dimension of 2L mm diameterA
Results for weight loss KῶF9 corrosion rate KɤF and percentage inhibition efficiency KɲF for VTU mixture and mild steel from the weight loss experiments in G
{dsorption of VTU molecules onto the mild steel surface blocked the active sites where the dissolution and release of metal cations into the solution occurs as a result of the action of sulphates and chloride anions- The surface charge on metal oxides in contact with aqueous solutions arises from structural charge associated with the terminal oxygen and metal atoms at the mineral surface that have unsatisfied valence9 as well as ions from the solution that associate with these terminal atoms in order to saturate this unsatisfied valence K26F

Summary

Introduction

Mild steel is one of the most applicable construction materialsB extensively used in chemicalB petroleumB automotiveB energy generating and allied industries for applications that are exposed to acidsB alkalis and salty environments such as acid cleaningB picklingB descalingB industrial acid cleaningB cleaning of oil refinery equipmentB heat exchangers and oil well acidizing D1PA It is the cheapestB most common and most versatile form of steel serving for every application that requires huge amount of steel as it provides material properties that are acceptable for many applicationsA it is weakly resistant to pitting and general corrosionB thusB it is continually replaced after being severely degraded in the corrosive environment during applicationACorrosion represents a significant cost burden and major industrial setback to the economy of every countryU it is the largest single cause of plant and equipment breakdown in process industriesA For a variety of industrial applicationsB it is possible the selection of construction materials which are completely resistant to corrosion from corrosive fluidsB but the cost of such an approach is most often restrictive D2PA Current reviews show that the most realistic cost of corrosion could be as high as S3 of the gross domestic product DGDPP of countries which have significant corrosion control measures in place D3B 4PA Numerous research and field experience over the decades have developed effective chemical treatments and corrosion control in so many applications from the transport of petrochemical products to the mining and processing of refractory oresA Despite the knowledge acquiredB it is evident that there is a gap in information of applications in more challenging environments and in the development and application of novel chemical compounds and treatment practicesA The chemicalsB known as corrosion inhibitorsB are continually fed into aqueous environments with the objective reacting with the metal surface to produce a passive protective chemical film D5-7PAThe mechanism of inhibitor adsorption and the relationship between inhibitor molecular structures and their adsorption properties is of great importance in corrosion inhibition studies D8PA Chemical compounds with functional groups containing heteroatoms within their molecular structure are capable of donating lone pair of electronsB important attribute of organic compounds in metal corrosion inhibitionAThe use of organic compounds for corrosion inhibition of ferrous alloys in different acidic medium has been studied by different authorsA The corrosion inhibiting property of these compounds is attributed to their molecular structure D9-11PA Bouklah et al D12P and Bentiss et al D13P showed that the adsorption of organic inhibitors mainly depends on physicochemical and electronic characteristics of the inhibitor moleculeB associated with their functional groupsB steric effectsB electron density of donor atomsB and the π-orbital character of donating electronsA A good inhibitor decreases the anodic and/or cathodic reaction of the corrosion processB the transport rate of the corrosive anions to the surface of the metalB and the potential difference at various sites on the metal surfaceA Inhibitors are basically easy to apply and offer the advantage of in-situ applicationATo further contribute to the study of the use of low cost chemical compounds for corrosion inhibition of ferrous alloys and deeper understanding of their inhibition mechanismB this research aimed to investigate the inhibiting influence of the synergistic effect of Whydroxy-S-methoxybenzaldehyde and 2BS-diphenyl-0-thiourea on mild steel corrosion in 2 M H0SOW and HCl acid solution through weight loss analysisB potentiodynamic polarization test and optical microscopyA. The use of organic compounds for corrosion inhibition of ferrous alloys in different acidic medium has been studied by different authorsA The corrosion inhibiting property of these compounds is attributed to their molecular structure D9-11PA Bouklah et al D12P and Bentiss et al D13P showed that the adsorption of organic inhibitors mainly depends on physicochemical and electronic characteristics of the inhibitor moleculeB associated with their functional groupsB steric effectsB electron density of donor atomsB and the π-orbital character of donating electronsA A good inhibitor decreases the anodic and/or cathodic reaction of the corrosion processB the transport rate of the corrosive anions to the surface of the metalB and the potential difference at various sites on the metal surfaceA Inhibitors are basically easy to apply and offer the advantage of in-situ applicationA.

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