Polarized Neutron Reflectometry of Nickel Corrosion Inhibitors.

Polarized neutron reflectometry has been used to investigate the detailed adsorption behavior and corrosion inhibition mechanism of two surfactants on a nickel surface under acidic conditions. Both the corrosion of the nickel surface and the structure of the adsorbed surfactant layer could be monitored in situ by the use of different solvent contrasts. Layer thicknesses and roughnesses were evaluated over a range of pH values, showing distinctly the superior corrosion inhibition of one negatively charged surfactant (sodium dodecyl sulfate) compared to a positively charged example (dodecyl trimethylammonium bromide) due to its stronger binding interaction with the surface. It was found that adequate corrosion inhibition occurs at significantly less than full surface coverage.X-ray photoelectron spectra were obtained at the National Engineering and Physical Sciences Research Council (EPSRC) XPS User’s Service (NEXUS) at Newcastle University, an EPSRC midrange facility. NR data were obtained on the D17 instrument, and samples were treated in the laboratories of the Partnership for Soft Condensed Matter (PSCM) at the Institut Laue-Langevin. M.H.W. is grateful for funding from the Oppenheimer Trust.This is the final version of the article. It first appeared from the American Chemical Society via http://dx.doi.org/10.1021/acs.langmuir.5b0171

Cobalt(III) complexes of macrocyclic-bidentate type as a new group of corrosion inhibitors for iron in perchloric acid, Corros

Abstract A new class of corrosion inhibitors for iron demonstrated by group of cobalt complex compounds, of the general formula [Co III (Rdtc)cyclam](ClO 4 ) 2 (1)-(4) where cyclam is 1,4,8,11-tetraazacyclotetradecane and Rdtc À refer to piperidine-, 2-, 3-or 4-methylpiperidine-dithiocarbamates, respectively, has been studied. Investigation of inhibiting properties of the ligands themselves as well as their corresponding complexes with Co(III) ion, was performed in 0.1 M HClO 4 by potentiodynamic polarization and EIS measurements. Cobalt complexes inhibit the corrosion of iron better than the uncomplexed ligands. Polarization curves suggest that complexes and amino-ligands are mixed-type and cathodic-type inhibitors, respectively. The impedance of the inhibited substrate increased with increasing concentration of inhibitor. An equivalent circuit is suggested, based on the analysis of EIS spectra. Using molecular modeling calculations, the complex compounds were characterized in terms of their structural properties and inhibition activity