Abstract
Dapsone derivatives Viz., 4, 4’-sulfonylbis(N-((1H-pyrrol-2-yl)methylene)aniline) (SBPMA) and 2-dimethylamino-5-[(4-{4-[(4-dimethylamino-benzylidene)-amino]-benzenesulfonyl}-phenylimino)-methyl]-benzene (DBBPB), a new class of corrosion inhibitors have been synthesized and their corrosion inhibition efficiency on mild steel in 0.5 M H2SO4 was investigated by mass loss, Tafel polarization and AC impedance measurements. Potentiodynamic polarization studies showed that, these compounds behave as mixed type of corrosion inhibitors. The adsorption process was found to obey Langmuir isotherm model. Electrochemical impedance spectroscopy (EIS) studies revealed that polarization resistance (RP) increases and double layer capacitance (Cdl) decreases as the concentration of the inhibitors increases. Various thermodynamic parameters for the adsorption of inhibitors on mild steel were computed and discussed. FTIR, EDX and SEM analyses were performed to study the film persistency of the inhibitors.
Highlights
Mild steel (MS) is an alloy of iron, carbon and several other elements, which hardens above its critical temperature, and is a class of strong, tough and low cost steel with an excellent mechanical property
This study reports the inhibitive effect of two newly synthesized dapsone derivatives such as 4, 4’-sulfonylbis(N((1H-pyrrol-2-yl)methylene)aniline) (SBPMA) and 2-dimethylamino-5-[(4-{4-[(4-dimethylamino-benzylidene)-amino]benzenesulfonyl}-phenylimino)-methyl]-benzene (DBBPB) on the corrosion of MS in 0.5 M H2SO4 using mass loss and electrochemical techniques
There is no appreciable increase in the inhibition efficiency after 5 hr of immersion time, this is due to desorption of the inhibitor molecules from the metal surface with increasing immersion time and instability of inhibitor film on the metal surface [29, 30]
Summary
Mild steel (MS) is an alloy of iron, carbon and several other elements, which hardens above its critical temperature, and is a class of strong, tough and low cost steel with an excellent mechanical property It has good physical and chemical properties such as toughness, welding, stamping and cutting performance. It is the most extensively used alloy in a wide spread spectrum of many industrial units for structural, instrumental and automobile applications. It is highly susceptible for corrosion in humid air especially in acidic media [1]. Corrosion inhibitors block the active sites and enhance the adsorption process, decreasing the rate of dissolution and extending the life span of the equipment [8, 9]
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