Porphyrins as Corrosion Inhibitors for N80 Steel in 3.5% NaCl Solution: Electrochemical, Quantum Chemical, QSAR and Monte Carlo Simulations Studies

Abstract

Abstract:The inhibition of the corrosion of N80 steel in 3.5 wt. % NaCl solution saturated with CO2 by four porphyrins, namely 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphyrin OPEN ACCESSMolecules 2015, 20 15123 (HPTB), 5,10,15,4,4′,4″,10,15,tetrakis(benzoic acid) (THP) and 5,10,15,20-tetraphenyl-21H,23H-porphyrin (TPP) was studied using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, scanning electrochemical microscopy (SECM) and scanning electron microscopy (SEM) techniques. The results showed that the inhibition efficiency, η% increases with increasing concentration of the inhibitors. The EIS results revealed that the N80 steel surface with adsorbed porphyrins exhibited non-ideal capacitive behaviour with reduced charge transfer activity. Potentiodynamic polarization measurements indicated that the studied porphyrins acted as mixed type inhibitors. The SECM results confirmed the adsorption of the porphyrins on N80 steel thereby forming a relatively insulated surface. The SEM also confirmed the formation of protective films of the porphyrins on N80 steel surface thereby protecting the surface from direct acid attack. Quantum chemical calculations, quantitative structure activity relationship (QSAR) were also carried out on the studied porphyrins and the results showed that the corrosion inhibition performances of the porphyrins could be related to their EHOMO, ELUMO, ω, and μ values. Monte Carlo simulation studies showed that THP has the highest adsorption energy, while T4PP has the least adsorption energy in agreement with the values of σ from quantum chemical calculations.

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“…3e,f ), which consist of R s (solution resistance), R p (polarization resistance), CPE (constant phase element) and R L (inductive resistance) and L (inductance) 33 . The presence of L in the impedance spectra in the presence of the inhibitors that were investigated indicated that iron was still dissolved by the direct charge transfer at the inhibitor adsorbed electrode surface 34 . The impedance of the constant phase element is given by the following equation: where Y o is the magnitude of CPE, j is the square root of −1, and n is the phase shift, which can be used as a gauge of the heterogeneity or roughness of the surface, and ω is the angular frequency 35 .…”

Acridine-based thiosemicarbazones as novel inhibitors of mild steel corrosion in 1 M HCl: synthesis, electrochemical, DFT and Monte Carlo simulation studies

“…Furthermore, steric factors and the type of functional groups present in a compound used as inhibitors are also very important. [12][13][14][15] Acridine derivatives, which are widely used as antibacterial and antiprotozoal agents are the derivatives of tricyclic nitrogen heterocyclic compounds. 16 Acridine derivatives are reported to have unique physical and chemical properties, biological activities, and industrial applications.…”

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“…It is also extracted from the figure that inhibition efficiency of PF-2 (93%) is more than that of PF-1 (85%). 29…”

“…The calculated values of the corrosion current density ( I corr ), corrosion potential ( E corr ), cathodic/anodic Tafel slopes ( b c , b a ), and inhibition efficiency (η %) are shown in Table 3. 29…”