Synthesis and characterization of Trimethoprim metal complexes used as corrosion inhibitors for carbon steel in acid media

• F.M. Ibrahim, R.A.Hammza and D.H. Fadhil

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

Abstract: Trimethoprim (TM) is an antibiotic used to treat bacterial infections as well as it is a heterocyclic compound, whose structure consists of 1,2,3-trimethoxybenzene and pyrimidine-2,4-diamine, therefore it can be used as a corrosion inhibitor due to easy production and low price on carbon steel in acidic media by adsorption process. Cr(III), Mn(II), Co(II), Ni(II) and Cu(II) complexes of Trimethoprim were synthesized and also used as a corrosion inhibitor. The Trimethoprim drug and its complexes were characterized by different spectroscopic methods: Ultraviolet-visible, Fourier transform infrared, conductivity measurements, thermal analysis (TG) and magnetic susceptibility measurement. Adsorption process can be attributed to changes in concentration of inhibitors with the acidity of a solution as well as the surface of the metal (carbon steel). The results of the experiment have shown the coordination of the Trimethoprim drug with the transition metal ions through nitrogen of pyrimidinyl ring so that square planar geometry was suggested for Mn(II), Ni(II), Cu(II) complexes while the Cr(III), Co(II) complexes have an octahedral geometry and these complexes have electrolyte properties. Corrosion inhibition on carbon steel was studied using weight loss method in one molar hydrochloric acid solution by organic inhibitor Trimethoprim and inorganic inhibitors (complexes) at different concentrations with different periods of time. The measurements have shown that Trimethoprim reduced the corrosion of the carbon steel surface and also the inhibition efficiency of the complexes increased with increasing concentration. The inhibition efficiency followed the order Co > Cu > Cr in one molar acidic solution.

Keywords: metal complexes of Trimethoprim, weight loss method, corrosion inhibitor

Int. J. Corros. Scale Inhib., 2019, 8, no. 3, 733-742 PDF (623 K)
doi: 10.17675/2305-6894-2019-8-3-20

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