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The corrosion behavior of Al in 1 M HCl solution with and without thiophene derivatives is studied utilizing altered chemical and electrochemical methods. Thiophene derivatives have been prepared and characterized by infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectral studies. The corrosion data were obtained using weight reduction and electrochemical techniques. The outcome data revealed that the efficiency rises with improving the dose of thiophene derivatives in aggressive solution, while it lowered with the rise of temperature. The adsorption of the studied thiophene derivatives on the surface of Al follows Langmuir isotherm. The thermodynamic parameters such as adsorption constant Kads and free energy of adsorption ( $$\Delta G_{{{\text{ads}}}}^{^\circ }$$ ) are calculated and discussed. Polarization curves indicated that the thiophene derivatives are mixed-kind inhibitors. The quantum calculation such as EHOMO, ELUMO and ΔE were obtained and related to the experimental data. The biological effect of these derivatives also discussed.

Expired Famotidine was tested as a corrosion protection for α-brass in 1 M HCl using modified methods: weight loss (WL), Tafel polarization (TP), AC impedance spectra (EIS) and electrochemical frequency modulation (EFM). The polarization resistance (Rp) data increased with increasing famotidine dose. The inhibition efficiency (IE) improved with raising famotidine concentration. The maximum IE of 90% has been achieved at 300 ppm. On the other hand, the efficiency lowered with temperature increased. The outcome data obtained revealed that famotidine performed excellently as a corrosion inhibitor for α‑brass in this medium at dissimilar temperatures. The surface of α-brass was tested utilizing scanning electron microscope (SEM), energy dispersion spectroscopy X-ray spectra (EDX), Fourier transform infrared spectroscopy (FT–IR), and atomic force microscopy (AFM analysis).

The influence of corrosion inhibition of some thiazole derivatives, namely: 2-(3,5-dimethyl-4-(p-tolyldiazenyl)-1H-pyrazole-1-yl)thiazol-5(4H)-one, 2-(3,5-dimethyl-4(phenyldiazenyl)-1H-pyrazole-1-yl)thiazol-5(4H)-one, and 2-(4-((4-chlorophenyl)diazenyl)-3,5-dimethyl-1H-pyrazole-1-yl)thiazol-5(4H)-one on Zn in 1.0 M HCl solution was studied by utilizing electrochemical and non-electrochemical tests. The obtained data without and with these derivatives were utilized to measure the protection efficiency (η %) which rises with the rise in the concentration of these derivatives. The phenomenon of physical adsorption was proposed and inhibitors adsorption was established to adapt Langmuir adsorption isotherm. Polarization data clearly indicated that these derivatives behaved as mixed inhibitors.

The inhibiting effect of the expired meloxicam on the corrosion of mild steel (MS) in 1 M HCl was tested by the weight loss, electrochemical frequency modulation, potentiodynamic polarization (PP) and electrochemical impedance spectroscopy techniques. The PP curves showed that this drug acts as mixed type inhibitor. This drug was adsorbed chemically on the MS surface following the Temkin adsorption isotherm. Some thermodynamic parameters were computed and discussed. The results indicated that the protection efficiency increases by raising both the doses of the inhibitor and the temperature of the medium. The morphology of the MS surface was analyzed by scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy. All of the obtained results from different techniques are similar.

Novel anionic 4-tert-Octylphenol Ethoxylated Phosphate Dipotassium salt (ethoxylated with 5 moles of ethylene oxide) surfactant was prepared and designated as OP-5-EO-K2PO, was characterized for its structure using spectroscopic measurements, in addition, its surface properties were investigated. The results indicated that OP-5-EO-K2PO exhibits excellent surface activity. Evaluation of the prepared surfactant as a corrosion inhibitor was carried out. The inhibition effect of OP-5-EO-K2PO surfactant, on the corrosion of C-steel in 0.5 M HCl was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. It was found that the novel anionic surfactant acts as effective inhibitor and its inhibition efficiency was significantly increased with increasing concentration. Polarization curves revealed that the novel prepared anionic surfactant represents mixed-type inhibitors. Adsorption of the investigated surfactant led to a reduction in the double layer capacitance and an increase in the charge transfer resistance.

This study targets the investigation of three pyrimidine-bichalcophene derivatives (MA-1230, MA-1231, MA-1232) for the prevention of corrosion on copper in 1 M HNO3 via weight loss (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) techniques. The surface morphology was also analyzed by different methods. It was found that the inhibition efficiency (% η) increased by increasing the doses of pyrimidine derivatives and the temperature of the medium. Weight loss data revealed the better adsorption of MA-1232 on the Cu surface at increased inhibitor dose, reaching a maximum efficiency of 99.14% at a dose of 21 μM at 45 °C. The best description of the adsorption of the investigated derivatives on the copper surface was given by the Langmuir isotherm. Some important thermodynamic parameters for the studied inhibitors were computed and are discussed herein. The polarization studies showed that the pyrimidine-bichalcophenes act as mixed inhibitors. Computational chemical approaches were used with informative yields, including quantum-chemical and molecular dynamics simulation techniques, which agree with the experimental results. The results obtained from all tested methods are strongly accepted.

The effect of Calotropis Procera (CP) extract on the corrosion inhibition of 304 stainless steel (SS) in 2 M HCl was studied using electrochemical (electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and electrochemical frequency modulation (EFM) and chemical weight loss (WL) methods at 25oC. The adsorption of the extract on 304 SS surface is consistent with Langmuir adsorption isotherm. The polarization plots revealed that the addition of extract shifts the cathodic and anodic branches towards lower currents. Such shifts indicate that CP extract acts as a mixed-type inhibitor. The thermodynamic parameters of activation and adsorption processes were calculated and discussed. The surface morphology of the 304 SS specimens was evaluating using different techniques.