Polyacrylamide (PAA) film was electrosynthesized on mild steel by cyclic voltammetry using a Ce(IV) saltoxalic acid initiator system. Polymerization was initiated by a free radical that is formed by fast reaction of oxalic acid and Ce(IV). The electrolysis of the solution results in regeneration of Ce(IV), which can oxidize the oxalic acid and produce radicals. The effect of temperature on the yield of the electroinitiated polymerization was studied. The potential sweep rate was changed to achieve polymer films with different levels of thickness. The capacity of the PAA film to protect mild steel from corrosion in an 1 M NaCl aqueous solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The structure of the PAA film on mild steel was investigated by physicochemical methods such as elemental analysis of C, H and N by a FTIR spectrometer. The results of the studies reveal that the corrosion resistance of PAA-coated mild steel is significantly higher and the corrosion rate considerably lower than for uncoated steel. PAA films formed with lower sweep rates exhibited a larger positive shift of the corrosion potential and greater charge transfer resistance, reflecting as higher inhibitors for corrosion of mild steel.
The inhibition performance of three selected dihydrazide derivatives, namely, malonic acid (MAD), succinic acid (SAD), and adipic acid (AAD) dihydrazide, was tested in relation to nickel corrosion in 1.0 M sulfuric acid (H2SO4) solution. Electrochemical methods (Tafel polarization, linear polarization resistance [LPR], and electrochemical impedance spectroscopy [EIS]) were used, complemented with scanning electron microscopy/energy-dispersive x-ray (SEM/EDX) examinations. Computational studies were also used to confirm experimental findings and to optimize the adsorption structures of dihydrazide derivatives. Results showed that the three tested dihydrazides inhibited Ni corrosion (mixed-type inhibitors) to an extent, depending on the type and concentration of the introduced inhibitor. SEM studies revealed that the corroded areas on the surface were decreased in the presence of additives to an extent, depending on the type and concentration of the tested inhibitor. Results obtained from electrochemical measurements are in good agreement with theoretical studies.
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