Adsorption, synergistic inhibitive potentials and quantum chemical studies of (E)-1-(2-((2,4-dimethoxyphenyl)diazenyl)phenyl)-2-hydroxy-2-phenylethan-1-one as mild steel anticorrosion agent in acidic medium

The azo dye, ((E)-1-(2-((2,4-dimethoxyphenyl)diazenyl)phenyl)-2-hydroxy-2-phenylethan-1-one) (DPP) was synthesized and characterized using spectroscopic techniques. The inhibition activities of DPP against mild steel corrosion were studied via experimental (using gravimetric, electrochemical techniques) and quantum chemical calculations. Synergism consideration was performed on DPP via experimental methods to investigate their inhibitive performance. The dye showed an inhibitory capacity of up to 83 % and in the presence of KI addictive, gave a performance of 93 %. The mechanism of adsorption obeys the Langmuir isotherm model, thus suggesting a complex adsorption mechanism for the inhibition process. The potentiodynamic polarization curve revealed that Ecorr shifts of DPP-mediated and KI-containing corrosive electrolytes (relative to the blank) were found to be below 85 mV suggesting a mixed-type corrosion inhibitor for the studied azo dye. The relative increment in Rct values and reduction in the Cdl values from impedance analysis was a result of the improved degree of surface protection by the inhibitor molecule onto the mild steel surface. SEM/EDS analysis revealed the presence of a protective film suggesting that DPP molecules are deposited, actively protecting the mild steel surface. The results from experimental methods shows that there is an overall increased performance on the inhibitory capacity of the dye and addition of KI further increases the efficiency of DPP. Theoretical studies shows that the strength of the azo dyes is in its electron donating and accepting ability, which is in consonance with the experimental findings.