5-Naphthylazo-8-hydroxyquinoline (5NA8HQ) as a novel corrosion inhibitor for mild steel in hydrochloric acid solution

Colloidal and interface aqueous chemistry of dyes: Past, present and future scenarios in corrosion mitigation

The most effective corrosion inhibitors are organic compounds, especially heterocyclic ones with a certain balance of hydrophilicity, hydrophobicity, and conjugation. Most dyes develop the critical characteristics of a substance that can be utilized as an effective corrosion inhibitor. These include the presence of polar functional groups, nonbonding electrons and multiple bonds of the aromatic ring(s) and side chains. In aqueous electrolytes, dyes efficiently bind to metal surfaces through their electron-rich spots, known as adsorption centers. Literature studies show that many dye series have excellent anticorrosive properties for many metal/electrolyte combinations. They contain many electron-donating sites and behave as polydentate and chelating ligands. The polar functional for instance -OH, -CONH₂, -NH₂, -OR, -SO₃H, -COOH, -NMe₂, -N=N-, -CHO, -N=C < etc. also help in solubilizing relatively complex dye molecules in aqueous electrolytes. This review work seeks to explain the interfacial adsorption of dye molecules and how that negatively affects metallic corrosion. Through their adsorption, dye molecules block the active sites. They mainly achieved this by employing the Langmuir isotherm model. Additionally, the mechanism of corrosion inhibition is investigated, with a special emphasis on dyes.

Experimental and computational investigations on the anti-corrosive and adsorption behavior of 7-N,N'-dialkyaminomethyl-8-Hydroxyquinolines on C40E steel surface in acidic medium

Two new 7-N,N'-dialkylaminomethyl-8-Hydroxyquinolines, namely 7-N,N'-dipropylaminomethyl-8-Hydroxyquinoline (DPQ) and 7-N,N'-dimethylaminomethyl-8-Hydroxyquinoline (DMQ), were synthesized and characterized using ¹H/¹³C NMR and Elemental analysis methods. Corrosion inhibition effect of DMP and DPQ for C40E steel in 1 M HCl was evaluated at different concentrations (10^-3 to 10^-6M) and temperatures (298 to 328 K) using several experimental and computational approaches. Weight loss and electrochemical studies showed that protection efficiencies (η_max) of DPQ and DMQ increase with increase in concentrations. The DPQ and DMQ showed maximum efficiencies of 96.1% and 94.4%, respectivelyat 10^-3 M. Polarization measurements showed that DMQ and DPQ act as mixed type corrosion inhibitors. Adsorption of DPQ and DMQ on C40E steel in 1 M HCl obeyed the Langmuir adsorption isotherm. Variation in surface morphology of corroded metallic surface with and without DMQ and DPQ was demonstrated using scanning electron microscopy. Molecular dynamics (MD) simulations studies showed that DPQ and DMQ acquire the flat or horizontal orientation over the C40E steel. DFT analyses revealed that both DPQ and DMQ interact with the C40E steelusing electron-sharing(donor-acceptor)mechanism. Computational analyses conducted using DFT and MD simulations well corroborate the experimental results.

Synthesis, characterization, and anti-corrosion properties of an 8-hydroxyquinoline derivative

A new 8-hydroxyquinoline derivative, namely 1,3-bis(quinoline-8-dimethylformamide) propane (BQYP), was synthesized and characterized by different spectral methods, such as ¹H NMR, ¹³C NMR, and FTIR spectra. The anticorrosive properties of the BQYP molecule against the corrosion of mild steel were tested in 2 M Η₂SO₄ acid with a varied range of concentrations (0.05–1 mM) at different temperatures using the electrochemical technique. It was clear that adsorption acted according to Langmuir's relationship. The inhibition effect improved with increases in concentration of inhibitor (~91% for 1 mM at 298 °K) and was reduced with increasing temperature. Finally, the density functional theory (DFT), with bases set according to the B3LYP/6-311+G (d,p) level, was used for calculating the quantum parameter to explain the effect of the electronic structure of the BQYP molecule on providing the experimental findings.

Comparative Evaluation of Anticorrosive Properties of Mahaleb Seed Extract on Carbon Steel in Two Acidic Solutions

Aqueous extract solution of Mahaleb seed (ASMS) was prepared using a simple and safe method. ASMS was tested to examine its potential to act as a green corrosion inhibitor for preventing the dissolution of Carbon steel in highly concentrated corrosive 2 M H₂SO₄ and 2 M H₃PO₄ using an electrochemical polarization Tafel plot and electrochemical impedance spectroscopy. ASMS provided a slight increase in the inhibition efficiency of H₃PO₄ (89%) compared with H₂SO₄ (86%). Fourier transform infrared spectroscopy (FTIR) and electronic scanning microscopy (SEM) were used to prove that adsorption of ASMS occurred on the metal surface. The thermodynamic adsorption and thermodynamic activation parameters were calculated at a range of concentrations and temperatures. The physisorption of ASMS followed the Langmuir adsorption isotherm (R² = 0.98). Finally, the role of ASMS as a protection mechanism was discussed.