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The inhibition of mild steel corrosion in 1 M HCl solution by some ionic liquids (ILs) namely, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate [HMIM][TfO], 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF4], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF6], and 1-hexyl-3-methylimidazolium iodide [HMIM][I] was investigated using electrochemical measurements, spectroscopic analyses and quantum chemical calculations. All the ILs showed appreciably high inhibition efficiency. At 303 K, the results of electrochemical measurements indicated that the studied ILs are mixed-type inhibitors. The adsorption studies showed that all the four ILs adsorb spontaneously on steel surface with [HMIM][TfO], [HMIM][BF4] and [HMIM][I] obeying Langmuir adsorption isotherm, while [HMIM][PF6] conformed better with Temkin adsorption isotherm. Spectroscopic analyses suggested the formation of Fe/ILs complexes. Some quantum chemical parameters were calculated to corroborate experimental results.

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The effect of surface treatment using NaOH or H2O2 on the bioactivity and corrosion behavior of AZX310, AZ91D, AM50, and AZ31 Mg alloys in simulated body fluid (SBF) has been studied with the aid of surface morphological assessment, in vitro characterization, and electrochemical measurements. The influence of immersion time on the behavior of the treated alloys in SBF was also investigated. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed successful surface modification upon treatment of alloy surface with NaOH and H2O2. XRD and SEM analyses also revealed that surface modification enhances formation and growth of hydroxyapatite (HA). Formation of HA layer on the alloy surface was further confirmed by Fourier transform infrared spectroscopy analysis. In vitro immersion test reveals that pH of SBF solution containing treated alloys is lower than that containing untreated alloy. However, pH increases with immersion time. Results from weight loss and electrochemical measurements indicate that treated alloys possess higher corrosion resistance in SBF than the untreated ones. H2O2 treated alloys demonstrated greater corrosion resistance in SBF than NaOH treated alloys.

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Abstract:The effects of seven macrocyclic compounds comprising four phthalocyanines (Pcs) namely 1,4,8,11,15,18,22,2,3,9,10,16,17,23,2,9,16, and 29H,31H-phthalocyanine (Pc4), and three naphthalocyanines namely 5,9,14,18,23,27,32,2,11,20, properties of the compounds were also investigated. All the studied compounds showed appreciable inhibition efficiencies, which decrease with increasing temperature from 30 °C to 70 °C. At each concentration of the inhibitor, addition of 0.1% KI increased the inhibition efficiency compared to the absence of KI indicating the occurrence of synergistic interactions between the studied molecules and I − ions. From the potentiodynamic polarization studies, the studied Pcs and nPcs are mixed type corrosion inhibitors both without and with addition of KI. The adsorption of the studied molecules on Al surface obeys the Langmuir adsorption isotherm, while the thermodynamic and kinetic parameters revealed that the adsorption of the studied compounds on Al surface is spontaneous and involves competitive physisorption and chemisorption mechanisms. The experimental results revealed the aggregated interactions between the inhibitor molecules and the results further indicated that the peripheral groups on the compounds affect these interactions. The calculated quantum chemical parameters and the QSAR results revealed the possibility of strong interactions between the studied inhibitors and metal surface. QSAR analysis on the quantum chemical parameters obtained with B3LYP/6-31G (d,p) method show that a combination of two quantum chemical parameters to form a composite index provides the best correlation with the experimental data.