Kinetics and mechanism of oxidation of two biologically reactive heterocyclic compounds, namely, barbituric (BA) and thiobarbituric (TBA) acids by chromium trioxide (CrVI) have been explored using UV–Vis absorption spectra in sulfuric and perchloric acid solutions at fixed ionic strength of 2.0 mol dm−3 and a temperature of 298 K. The oxidation reactions demonstrated a 3:4 stoichiometry (organic acid: CrVI). The reactions kinetics in the examined acidic media were set to be first order with admiration to [CrVI] and fractional orders in organic acid and H+ concentrations. Varying the ionic strengths and dielectric constants of the reaction media had no noteworthy influence on the reactions’ rates. Tests for free radicals involvement throughout the reactions were positive. Addition of chromium(III) as a predicted oxidation product did not considerably alter the rates whereas addition of manganese(II) diminished the oxidation rates. Supplementation of some divalent transition metal ions increased the oxidation rates. At same investigational circumstance, the rates of BA oxidation in both acidic media were set to be about 20–30% higher than those of TBA, and those acquired in sulfuric acid were also found to be higher than those of perchloric acid solutions for both BA and TBA with almost the same percentages. The oxidation products of BA and TBA were described as 2,4,5,6-pyrimidinetetraone (alloxan) and 2-thio-4,5,6-pyrimidinetrione, respectively. A conceivable oxidation mechanism has been anticipated. The derived rate-law expression was in a good agreement with the investigational outcomes. The activation parameters with regard to the second order rate constants were assessed and debated. The existing study presents an unprecedented simple and inexpensive treatment method for removal of certain pollutants for saving the environment and human health.

In this report, two chromotrope dyes, chromotropic acid (CA) and chromotrope 2R (CR), were explored as inhibitors against mild steel corrosion in 1.0 M sulfuric acid solutions at 303 K. Electrochemical, spectroscopic, chemical, and microscopic techniques, namely, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy, mass loss, and scanning electron microscopy (SEM), have been employed to evaluate the inhibition efficiencies (%IEs) of the examined organic dyes. The %IEs were found to increase with the inhibitors’ concentrations, while they decreased with rising temperature. The outcomes of the PDP technique displayed that the examined inhibitors operated as mixed-type inhibitors with anodic prevalence. The impedance spectra described by Nyquist and Bode graphs in the corrosive environment and in the presence of various concentrations of the examined inhibitors showed single depressed capacitive loops and one-time constants. This behavior signified that the mild steel corrosion was managed by the charge transfer process. The SEM micrographs of the surfaces of mild steel samples after adding the examined inhibitors revealed a wide coverage of these compounds on the steel surfaces. Thus, the acquired high %IEs of the examined inhibitors were interpreted by strong adsorption of the organic molecules on the mild steel surface. This constructed a shielding layer separating the alloy surface from the corrosive medium, and such adsorption was found to follow the Langmuir isotherm. Furthermore, the evaluated thermodynamic and kinetic parameters supported that the nature of such adsorption was mainly physical. Results obtained from all employed techniques were consistent with each other and revealed that the %IE of the CR inhibitor was slightly higher than that of CA under similar circumstances. Finally, the mechanisms of both corrosion of mild steel in sulfuric acid solutions and its inhibition by the tested organic dyes were also discussed.

Expired antibacterial drugs such as ampicillin (AMP) and Ceftriaxone (CRO) were used as anticorrosive for Sabic Fe corrosion in 1.0 M HCl solutions. Chemical and electrochemical methods were applied to confirm the performance of the inhibition of these drugs. The effectiveness of inhibition increases with an increased concentration of AMP and CRO drugs which also decreases with temperature. The inhibition performance of drugs owing to their adsorption on the Sabic iron surface through the Langmuir adsorption isotherm. Galvanostatic polarization demonstrated that the expired AMP and CRO act as mixed inhibitors. The thermodynamic function for activation and adsorption process was defined and interpreted. AMP and CRO drugs inhibit the pitting attack caused by the presence of chloride ions. Pitting potentials were transferred to more noble values that demonstrated that these drugs served as pitting corrosion inhibitors. All outcomes findings confirm that the AMP and CRO acted as excellent inhibitors for Sabic Fe corrosion in 1.0 M HCl solutions and the CRO is more efficient inhibitors than AMP at all the studied concentrations owing to its high molar mass. The quantum chemical calculations of the expired AMP and CRO drug molecules were done and discussed using density functional theory (DFT) method. The quantum chemical calculations and the results of the molecular dynamics simulation correlate well with experimental observations.

The inhibition impacts of two novel synthesized green biosurfactants (B-Surf.), namely, sodium Ndodecyl asparagine (AsS) and sodium N-dodecyl arginine (ArS), on the dissolution of mild steel alloy (MS-37-2), in aqueous sodium chloride solutions was inspected using various techniques. Increased concentration of NaCl solution resulted in an increase in the corrosion rate of MS-37- 2. Inhibition efficiencies of B-Surf. compounds were found to increased with increase inhibitor concentrations. The synergistic inhibition action between B-Surf. inhibitors and Zn2+, Al3+ and Ce4+ on the dissolution behavior of steel alloy in NaCl solutions was investigated and interpreted. The surface morphology of the MS-37-2 surface was observed using a scanning electron microscopy (SEM). This adsorption follows Langmuir isotherm. The evaluated thermodynamic functions supported the mechanism of physical adsorption of the inhibitors. The mechanisms of corrosion and its inhibition of MS-37-2 in NaCl solutions were interpreted.

The inhibitory impacts of two expired drugs, namely, azithromycin (AZM) and roxithromycin (RXM) towards the corrosion of mild steel (MS) in 1.0 M H2SO4 solution were examined exploiting potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss techniques. The results obtained from various employed techniques indicate that increasing the concentration of examined expired drugs and reducing the temperature increased the inhibition efficiencies. Potentiodynamic polarization indicated that the expired AZM and RXM drugs acted as mixed-type inhibitors, but the cathode was highly polarized, βc > βa. The inhibiting power of these compounds is interpreted based on their adsorption on the surface of MS. The adsorption process obeys Langmuir isotherm. Impedance data confirmed that MS corrosion is under charge transfer control and the adsorption of both expired drugs on the MS surface led to the formation of protective film. The inhibition efficiency of RXM is greater than that of AZM due to the increased molecular weight and number of electron donating group within the expired drug. Activation and adsorption thermodynamics parameters were computed and interpreted. The adsorption process is spontaneous and endothermic.

The inhibitory vigor of two polymer molecules namely, polyethylene glycol (PEG) and polyvinyl alcohol (PVA) against the corrosion of iron in 1.0 M NaCl was assessed by chemical and electrochemical technologies. All the computed corrosion parameters from all technologies confirm the inhibitory impact of PEG and PVA compounds. The anticorrosion efficiency increased with the concentration of the polymer molecules to reach 93% and 86% at 500-ppm concentration of PEG and PVA, respectively. The potentiodynamic polarization confirms that the two polymer molecules act as mixed inhibitors. The mechanism of the anticorrosion was explicated in terms of the spontaneous adsorption of these molecules on the iron interface according to the negative values of ∆G o ads. The surface morphology was revealed by SEM images and indicated the building of adsorbed film on the iron surface in the presence of PEG and PVA, which leads to the isolation of iron surface from the corroded NaCl solution. The activation and the adsorption thermodynamics parameters was determined and explicated

The inhibition of mild steel corrosion in sulfuric acid environment was evaluated by citrulline and glutamine at fixed temperatures. The tools used for this evaluation were potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and mass loss (ML) measurements. Also, the morphology of mild steel surfaces was examined prior to and after corrosion adding the tested inhibitors by scanning electron microscopy (SEM). The evaluated inhibition efficiencies (% IEs) of the tested inhibitors increased with their concentrations but decreased with increasing sulfuric acid concentration. Results of PDP technique indicated that the examined compounds behaved as mixed inhibitors with cathodic majority. ML studies revealed that % IEs reduced with increasing temperature. The investigational results acquired from all utilized techniques are agreeable with each others which disclosed that the %IEs of citrulline were higher than glutamine under comparable conditions. The acquired great % IEs of the tested inhibitors was understood on the basis of strong adsorption of amino acids on mild steel surface creating a defensive layer and this adsorption was noticed to accord with Langmuir isotherm. Thermodynamic and kinetic parameters were computed and discussed which confirm the physical adsorption mechanism of the examined inhibitors. The kinetics of the corrosion inhibition by such compounds revealed negative first order of corrosion inhibition process demonstrating the acquired great % IEs of the investigated compounds.

The anti-corrosion efficacies of two polymeric molecules, polyvinyl alcohol (PVA) and alginic acid (AA), on the corrosion of SABIC type-X60 carbon steel (CSX60) in 1.0 M HCl solutions were investigated. Chemical and electrochemical techniques, such as weight loss analysis, galvanostatic polarization, potentiodynamic anodic polarization (PDAP), and electrochemical impedance spectroscopy were employed. The results of these experiments revealed that the anti-corrosion activities increased with decreasing temperatures and increasing concentrations of PVA and AA. The surface morphologies of the investigated steel surfaces were analyzed via scanning electron microscopy. The anti-corrosive strengths of the polymeric molecules with respect to the general and pitting corrosion behavior were demonstrated via the formation of adsorbent films that isolated the CSX60 surface from the aggressive acidic solutions. The inhibitor adsorption followed the Langmuir isotherm model. A few thermodynamic activation parameters were also calculated and discussed. PVA and AA were found to retard the pitting corrosion of CSX60 based on the shift of pitting potential to a nobler direction in the PDAP profiles.

Although antibiotics are fundamentally vital for treating human diseases, they became harmful to the ecosystem if they reach to the environment. Due to antibiotics are intensely vulnerable to oxidation, oxidation of antibiotics can be considered as a recognized tool for removal or degradation of antibiotics to save the humans and ecosystem. The existing research illuminates the kinetics of oxidative degradation of sulfafurazole antibiotic (SFZ) using chromium trioxide (CrO3) in both H2SO4 and HClO4 media. The reactions in both acidic media showed a 1: 1.33±0.07 stoichiometry (SFZ: CrO3). The reliance of the rates of oxidation reactions on the reactants’ concentrations illuminated that the reactions were frst order in [CrO3], whereas in [SFZ] and [H+], their orders were fractional-frst and fractional-second, respectively. The rate of oxidation of SFZ in H2SO4 was discovered to be higher than that observed in HClO4. The oxidation rates were not infuenced by the change in ionic strength (I) or dielectric constant (D). Addition of Cr(III) had not remarked efect on the rates. Free radical intervention tests were positive. The activation quantities were calculated then discussed. A conceivable mechanism of oxidation was anticipated. Furthermore, the rate-law expressions were also derived

Via electrochemical approach, the effect of [4-(4-chloro-phenylazo)-3-hydroxy-5-phenylamino-thiophen-2-yl]- phenyl-methanone (TD) as a corrosion inhibitor for the corrosion of carbon steel (CS) in 1.0 M HCl solution has been demonstrated. Electrochemical examination, surface analysis, and theoretical studies (quantum chemistry and molecular dynamic) were used to examine the efficiency of the inhibitor. Both inhibitor concentration and temperature were found to induce inhibitory responses. According to the findings, this compound acts as a mixed-type inhibitor. It also behaves according to the Langmuir and Henry adsorption isotherms. Thermodynamic parameters were calculated and discussed. Polarization data showed that the examined compounds significantly adsorbed on the steel surface, which rises the inhibition efficiency up to 95 % in the presence of 5 × 10−5 M at 25°C. The predicted molecular dynamics (MD) simulation and quantum chemistry results revealed good consistency with the experimental work