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A new nonionic surfactant (NIS), namely, 17-hydroxy-3,6,9,12,15-pentaoxaheptadecyl-5- ((4-(((17-hydroxy-3,6,9,12,15-penta oxa hepta decyl) oxy) sulfonyl) phenyl) diazenyl)-2-(2-oxo-2H- chromene-3-carboxamido) benzene sulfonate was synthesized based on condensation reaction between an azo dye and polyethylene glycol. The chemical structure was elucidated from IR and 1H NMR spectral data and surface activity was measured. The inhibitive effect of the resultant NIS toward corrosion of steel in 1.0 M HCl was evaluated by potentiodynamic polarization, impedance spectroscopy (EIS), non-electrochemical methods (weight loss), surface morphology (SEM and EDX) and DFT calculations. The anti-corrosion performance showed an optimal efficiency of 96.04% at the concentration of 7.50 × 10−4 M from polarization measurements. Both the anodic and cathodic inhibition were acquired from Tafel plots polarizations (TFP). The adsorption of NIS onto steel surface obeyed Langmuir isotherm. In addition, SEM images showed higher surface protection in presence of inhibitor in agreement with a molecular dynamic simulation which exhibited optimal surface alignment between inhibitor and steel. A good agreement between electrochemical methods and DFT calculations was achieved. [ABSTRACT FROM AUTHOR]

Tetraethyl orthosilicate (TEOS) was used as a chemical precursor to deposit ultra-thin SiOxCy plasma polymer films onto mild steel surfaces for preventing the corrosion process. The structure--property relationships of the coatings were evaluated by X-ray Photo Spectroscopy (XPS), X-Ray Diffraction (XRD), Fourier Transform InfraRed spectroscopy (ATR-FTIR) and Energy Dispersive X-ray spectroscopy (EDX) completed with Scanning Electron Microscopy (SEM). The SEM micrographs confirmed a pinhole-free surface morphology of the low-pressure deposited plasma polymer films. The TEOS molecules become fragmented in the plasma by numerous collisions with energy-rich electrons and heavier particles. Recombination of fragments and condensation onto the steel substrate is responsible for the formation of organic SiO containing plasma polymer layers. Such thin layers consist of predominantly SiOx structures. Their properties are determined largely by the gap distance between the two samples used as electrodes in the plasma. The efficiency of the corrosion-protecting coating was compared with uncoated samples. The corrosion protection was determined by exposure of samples to 3.5% NaCl aqueous solutions. For this purpose, polarization and Electrochemical Impedance Spectroscopy (EIS) were used to monitor the corrosion. The optimal gap distance between the electrodes was determined for corrosion protection. The best protective efficiency reached more than 97% of the total protection as measured at room temperature. [ABSTRACT FROM AUTHOR]