Abstract
Divalent cobalt and copper chelates of the two ligands 1-(1-ethoxycarbonylmethyl-2-oxoindolin-3-ylidene) thiosemicarbazide ( EOIT ) and 1-(1-benzyl-2-oxoindolin-3-ylidene) thiosemicarbazide ( BOIT ) are the target compounds of the current study. Identification of the structures and geometries of these compounds have been performed using the possible physicochemical and analytical instruments. Elemental analysis, molar conductance and thermal analysis assured the composition of the four chelates to be [Co(BOIT)Cl]•1·.5H 2 O ( BOIT-Co ), [Cu(BOIT)Cl] ( BOIT-Cu ), [Co(EOIT)Cl 2 (H 2 O)]•5H 2 O ( EOIT-Co ) and [Cu(EOIT)Cl]•Cl ( EOIT-Cu ) which was further confirmed by the measurement of mass spectra. The architecture arrangement of the ligand atoms around Co and Cu centers has been determined depending on the UV–Vis spectral measurements and calculation of µ eff values. This proved that the copper compounds were square planer whereas the cobalt complexes were tetrahedral or octahedral arrangements. These compounds were examined as corrosion inhibitors for Sabic iron in 1.0 M HCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy, mass-loss and scanning electron microscopy techniques. The acquired outcomes disclosed that the examined compounds were found to have high inhibition efficiencies (% IEs) which were dependent on their concentrations and composition. The obtained high % IEs (83–87% at concentration of 400 mg/l) were interpreted by strong adsorption of the compounds’ molecules on the iron surface and such adsorption was discovered to follow Langmuir adsorption isotherm. At the same concentration, the % IEs are slightly increased in the order: EOIT-Cu > BOIT-Cu > EOIT-Co > BOIT-Co . Finally, the investigational results obtained from all employed techniques were in a good consistent with each other.
Highlights
Iron and its alloys have numerous applications in industry and machinery due to their excellent mechanical properties
These compounds were examined as corrosion inhibitors for the Sabic steel in 1.0 M HCl utilizing potentiodynamic polarization, electrochemical impedance spectroscopy, mass-loss method and scanning electron microscopy at fixed temperature of 298 K
The IR and mass spectra assured the coordination of the ligands to the Co or Cu centers as OSN tridentate monobasic thiol (i.e. EOIT-Co) or neutral thione (i.e. EOIT-Cu, BOIT-Co and EOIT-Cu) modes of bonds
Summary
Iron and its alloys have numerous applications in industry and machinery due to their excellent mechanical properties. They are subjected to corrosion phenomenon in various media [1,2,3]. Corrosion phenomenon is a naturally occurring process [4, 5], which causes a deterioration of significant properties in metals and alloys, weakening of buildings and machinery, corrosion of petroleum pipeline, etc. As an example, iron rust and its alloys is regarded as a serious industrial problem in acidic media [6,7,8] because acidic media are widely utilized in numerous applications such as industrial cleaning, acid discaling, pickling of steels, petroleum processes, etc. It is indispensable to preserve metals and alloys from the harmful effect of corrosion phenomenon in different environments [9]
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