Inhibition efficiency and corrosion rate studies of mild steel in nitric acid using 2-thioacetic acid–5-pyridyl-1,3,4-oxadiazole complexes

• Dina A. Najeeb

Department of Chemistry, College of Science, Al-Nahrain University, Baghdad, Iraq

Abstract: The Schiff base 2-thioacetic acid–5-pyridyl-1,3,4-oxadiazole and its complexes with metal ions Ni(II), Cu(II) and Co(II) have been examined as corrosion inhibitors of mild steel in 1 N HNO₃ solution by using weight loss technique. Data that we obtain shows good performance that these compounds are good inhibitors. The inhibition efficiency for the prepared ligand and its metal complexes increases with increasing their concentrations. The surface coverage values increase with increasing inhibitors concentration. The corrosion rate decreases as the concentrations of the ligand and its metal complexes increase. The inhibition efficiency of the ligand is less than that of its metal complexes and the inhibition efficiency of the metals follows the order Co>Ni>Cu. In the industries the inhibitors used widely due to anti-corrosive properties, but secondary effects may be shown which damage the environment. So the researchers began to prepare environmentally friendly inhibitors, like the prepared ligand and its metal complexes. At this time, some inhibitors are not being used in industrial processes due to their toxicity of chromate, phosphate and arsenic compounds, referring to different environmental and health troubles, so the governments must impose strict international laws. Inhibition behavior of the prepared ligand and its metal complexes has been attributed to their adsorption on the steel surfaces. The adsorption of the inhibitors obeys Langmuir adsorption isotherm for all tested systems. The surface morphology of mild steel was checked using a scanning electron microscope.

Keywords: corrosion, inhibition, mild steel, nitric acid, adsorption

Int. J. Corros. Scale Inhib., 2019, 8, no. 3, 717-725 PDF (1 090 K)
doi: 10.17675/2305-6894-2019-8-3-18

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