Volume 60 (2016): Edizione 3 (September 2016)

Concentrating of pore bentonite water as a result of water evaporation at the hot container surface is expected when the bentonite cover of the permanent nuclear waste container is being gradually saturated. The study assesses the influence of an extent of the pore water enrichment by chloride and sulphate ions up to a multiple of a hundred of their equilibrium concentration. An increase of concentration of these ions does not imply an increase of the electrolyte aggressivity automatically. A minimum of corrosion resistance was observed at triplicate concentration at all temperatures, 40, 70 and 90°C. Even more significant impact on corrosion behaviour was recognized for composition of anoxic atmosphere above the electrolyte. Contrary to nitrogen, the mixture of nitrogen and carbon dioxide remarkably elevates the electrolyte’s corrosion aggressivity.

This article focuses on corrosion of the steel reinforcement in the concrete where the blast or demetalized steelmaking slag as one of the components for fabrication was used. The slag from iron and steel production from U.S. Steel Kosice was used in the experiment. Steel reinforcement type S 235 (STN 11 375) were made by cold drawing. Chemical composition of slag in form of powder and slag leachates was analysed using X-ray fl uorescence spectrometry. Corrosion tests were carried out by measuring the polarization curves based on potentiodynamic polarization of steel samples exposed in leachate and also by polarization resistance method directly on the steel embedded in concrete and exposed in atmospheric precipitation. The results revealed differences in the corrosion rate, depending on chemical composition of the slag, which is closely related to its metallic and sulphur content.

Adsorption thermodynamics and kinetics of Azure C and from the aqueous solution on activated charcoal was examined. The charcoal was activated by concentrated sulphuric acid and the adsorption kinetic and thermodynamic was tested in batch experiment. An experiments used the adsorption batch method to observe the effect of the variable parameters, i.e. concentration of dye, time of contact, pH, temperature and adsorbent dose. The ideal dosage of adsorbent was 0.3 g for Azure C. The equilibrium state was reached within 60 min for dye Azure C at activated charcoal. The isotherms of equilibrium were investigated to characterize the adsorption operation. The data for the kinetics study were adjusted utilizing the equation of pseudo- second-order and the model of diffusion (intra-particle). All data were evaluated by means of equilibrium Freundlich, Langmuir and Temkin isotherm on activated charcoal surface. Based on the adsorption isotherm evaluation on activated charcoal the result was 4S by using Giles classification. The thermodynamic factors like ΔH, ΔG and ΔS were estimated.

The study is focused on evaluating hydrogen charging of materials in plating baths approved for aviation and in weak acid plating baths. For the evaluation, ASTM F519, ASTM F326 and a newly patented method of measuring device PCN1 - Pulsator cyclic loading were used. ASTM F519 is time consuming and the results are difficult to compare. ASTM F326 proved to be unsuitable for testing above plating baths because of strong hydrogen embrittlement of probes and thus their destruction. Conversely, the PCN1 method was fast and reproducible. Results showed that the baths approved for aviation caused stronger hydrogen embrittlement than weakly acidic zinc baths.

The article summarizes state of the art of the influence of external layer of Fe-Zn intermetallics on corrosion behaviour of galvanized steel in a fresh, hardened and chloride contaminated concrete. Current point of view on formation, composition and crystallography of particular intermetallic Fe-Zn phases, that are present in hot dip galvanized coating. External factors as alloying elements are involved as well. A corrosion resistance of these intermetallic layers (especially ζ-FeZn₁₃) during exposure in concrete is evaluated finally.