Cobalt(III) complexes of macrocyclic-bidentate type as a new group of corrosion inhibitors for iron in perchloric acid, Corros

Abstract A new class of corrosion inhibitors for iron demonstrated by group of cobalt complex compounds, of the general formula [Co III (Rdtc)cyclam](ClO 4 ) 2 (1)-(4) where cyclam is 1,4,8,11-tetraazacyclotetradecane and Rdtc À refer to piperidine-, 2-, 3-or 4-methylpiperidine-dithiocarbamates, respectively, has been studied. Investigation of inhibiting properties of the ligands themselves as well as their corresponding complexes with Co(III) ion, was performed in 0.1 M HClO 4 by potentiodynamic polarization and EIS measurements. Cobalt complexes inhibit the corrosion of iron better than the uncomplexed ligands. Polarization curves suggest that complexes and amino-ligands are mixed-type and cathodic-type inhibitors, respectively. The impedance of the inhibited substrate increased with increasing concentration of inhibitor. An equivalent circuit is suggested, based on the analysis of EIS spectra. Using molecular modeling calculations, the complex compounds were characterized in terms of their structural properties and inhibition activity

Adsorption and inhibition effect of 2,4-diamino-6-hydroxypyrimidine for mild steel corrosion in HCl medium: experimental and theoretical investigation, Ionics

2,4-Diamino-6-hydroxypyrimidine (2D6H) was examined as corrosion inhibitor of mild steel (MS) in 0.1 M HCl using potentiodynamic measurements, linear polarization resistance (LPR), scanning electron microscopy, electrochemical experiments, and quantum chemical calculations. All measurements show that the corrosion inhibition effectiveness is forthright compared to the concentration of 2D6H ranging from 0.5 to 10.0 mM. Adsorption of 2D6H on the MS surface in the presence of HCl is determined to obey Langmuir adsorption isotherm. The electronic features elucidated by quantum chemical calculations were associated with the experimental inhibition productivities. The mechanism of inhibition was revealed by Epzc measurements