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The active corrosion protection of metallic substrates can be achieved by the addition of corrosion inhibitors to protective coatings. However, direct mixing of inhibitors with coating formulations can lead to important drawbacks, decreasing barrier properties of the coating and diminishing activity of the inhibitor. Nanocontainers for corrosion inhibitors were developed in this work using layered double hydroxides (LDH) as nanocarriers. The LDH were used as nanosized particles, which are then included in a sol-gel hybrid coating, and as a LDH layer directly formed on the metal surface (conversion film) and covered by a sol-gel hybrid layer. Electrochemical impedance spectroscopy (EIS) has been used for evaluation of corrosion protective properties of the coatings. The results show that the LDH with incorporated vanadate inhibitor provide efficient active corrosion protection in both cases. [ABSTRACT FROM AUTHOR]

A comparative X-ray diffraction study of the initial single-phase metal-oxide compound-strontium iron molybdate SrFeMoO (SFMO)-and that subjected to additional isothermal annealing shows that this heat treatment leads to the appearance of a SrMoO (SMO) phase. Small-angle neutron scattering measurements indicate that the SMO phase forms a dielectric shell surrounding SFMO grains, which has a characteristic thickness of 2-4 nm and extends above 120 nm. The character of the temperature dependence of the electric resistance corresponds to the metal-type conduction in single-phase SFMO and changes to a semiconductor type in the material with SMO dielectric shells, which is evidence of a tunneling mechanism of charge transfer. This conclusion is confirmed by an increase in the absolute value of the negative magnetoresistance of SFMO due to the appearance of a tunneling magnetoresistance component of the same sign. [ABSTRACT FROM AUTHOR]

Plasma Electrolytic Oxidation (PEO) coatings on AM50 were developed in electrolytes containing CeO2 particles. The effect of particle concentration in the electrolyte on the final microstructure of the coatings was studied and correlated with the corrosion behavior. CeO2 particles were incorporated into the coatings and located preferentially in pores and cracks. The process involves both uptake and reactive incorporation of CeO2 under local melting caused by microdischarges. The coating with the lower concentration of particles has the best corrosion properties as measured with EIS. Higher concentration of particles increased the defect density in the coating which has a negative effect on the corrosion resistance. [ABSTRACT FROM AUTHOR]

The principal possibility to grow layered double hydroxide (LDH) at ambient pressure on plasma electrolytic oxidation (PEO) treated magnesium alloy AZ91 in the presence of chelating agents is demonstrated for the first time. It avoids hydrothermal autoclave conditions, which strongly limit wide industrial application of such coating systems, and the presence of carbonate ions in the electrolyte, which lead to the formation of "passive" non-functionalizable LDH. A combination of chelating agents (sodium diethylenetriamine-pentaacetate (DTPA) and salicylate) were introduced to the treatment solution. The role of each additive and the influence of treatment bath composition on the LDH formation processes are discussed. A synergistic effect of DTPA and salicylate during LDH formation is discovered and its possible explanation is proposed. [ABSTRACT FROM AUTHOR]

The objective of this work is to investigate the scale of the effect of spontaneous solution evaporation during SVET (Scanning Vibrating Electrode Technique) measurements and demonstrate how it biases the final results. When SVET maps are continuously acquired for more than several hours, the measured currents are smaller than expected. This is attributed to solvent (typically water) evaporation which leads to an increase in solution conductivity over time. If this is not considered when converting the measured potential differences into the local current densities, the SVET results display currents smaller than the true ones. Here, this effect is studied with a platinum disk electrode as source of a constant current and a model corroding system consisting of the AA2024/CFRP galvanic couple. Corrective actions are proposed to mitigate the problem, either in the experimental set‐up or as numerical correction. [ABSTRACT FROM AUTHOR]