التحضير ودراسة مشتقات الباربيتورات الجديدة كمثبطات للتآكل

Synthesis and Investigation of New Barbiturate derivatives as corrosion inhibitors

Abstract

The subject of the current study is an electrochemical and study of the corrosion of carbon steel alloy using new barbiturate derivatives prepared from thiobarbituric acid as a starting material. The first is K2D2 (5-(4-(4-(((4 nitrophenyl) imino) methyl) phenoxy) benzylidene)-2-thioxo dihydropyrimidine-4,6(1H,5H)-dione) and the second is K2D3 (2-thioxo-5). -(4-(4-((m-tolylimino) methyl) phenoxy) benzylidene) dihydropyrimidine-4,6(1H,5H)-dione). as inhibitors at different concentrations of (0,25,50,100,150,200) ppm in 1M sulfuric acid solution with a temperature range of (303,313,323) K. The prepared compounds were characterized by FT-IR, 1H-NMR and 13C-NMR techniques. The experimental results obtained using a static stress device (potentiostat device) were discussed, including the slope of the polarization or anodic and cathodic taphel curves (βa, βc), The corrosion current density (Icorr), the corrosion voltage (Ecorr), and the percentage of inhibition efficiency (%E) were studied, in addition the study of the effect of temperature and concentration on the inhibition efficiency. The results show an increase in the inhibition efficiency with increasing temperature and concentration. It has been confirmed that the compounds that were prepared and used as inhibitors are effective and suitable inhibitors for resisting the corrosion process and protecting the steel alloy under experimental conditions. An inhibition efficiency of up to 92.9% was obtained for compound K2D2 and 87.8% for compound K2D3. The thermodynamic functions of the corrosion process (ΔG, ΔH, ΔS) were calculated, a negative value was obtained for the enthalpy, which indicates that the reaction heat emitter. The negative value for the Gibbs energy indicates the spontaneity of the reaction, and a negative value for the entropy indicates a decrease in the randomness of the system. The adsorption isotherms for the compounds used as inhibitors were extracted, it was found that they obey the Langmuir equation. The thermodynamic functions for adsorption (ΔGads, ΔHads, ΔSads). A negative value for the Gibbs energy which indicates that the adsorption process was spontaneous, and the enthalpy value is positive, meaning the reaction is endothermic, and the entropy is positive, which indicates an increase in the randomness of the system