Search Results

1 - 10 of 13 items

  • Author: M. Kouřil x
Clear All Modify Search
Protection of historical lead against acetic acid vapour

Abstract

Historical lead artefacts (small figurines, appliques, bull (metal seal) can be stored in depository and archives in inconvenient storage conditions. The wooden show-case or paper packagings release volatile organic compound to the air during their degradation. These acids, mainly acetic acid are very corrosive for lead. The thin layer of corrosion products which slows atmospheric corrosion is formed on lead surface in atmospheric condition. In presence of acetic acid vapour the voluminous corrosion products are formed and fall off the surface. These corrosion products do not have any protection ability. The lead could be protected against acid environment by layer of “metal soup” which is formed on surface after immersion in solution of salt of carboxylic acid for 24 hours. The solutions of acids (with vary long of carbon chain) and their salts are examined. Longer carbon chain provides better efficiency convers layer. The disadvantages are low solubility of carboxylic acids in water and bad abrasion resistance of formed layer.

Open access
Corrosion rate of cathodically "protected" steel in carbonate environment

Korozní rychlost katodicky "chráněné" oceli v prostředí uhličitanů

Jedním ze způsobů vysvětlení mechanizmu ochranné funkce katodické ochrany je katodická pasivace. Vlivem katodické reakce dochází v okolí úložného zařízení k alkalizaci půdy, která usnadňuje přechod železa do pasivního stavu. K zapasivování oceli však dojde pouze v případě, že vložený ochranný potenciál má kladnější hodnotu než pasivační potenciál. Cílem práce bylo určit závislost pasivačního potenciálu a korozní rychlosti na korozním potenciálu v prostředí uhličitanu s různým pH s využitím elektrochemických metod a rezistometrické techniky. Korozní rychlost železa při dlouhodobé expozici byla určena pomocí rezistometrického čidla. Hodnota pasivačního potenciálu klesá s rostoucí hodnotou pH. Ocel se v prostředí uhličitanu pasivuje při běžném ochranném potenciálu -850 mV/CSE dosažením pH 11. Pod touto hodnotou ocel koroduje v aktivním stavu, a to pro úložná zařízení nepřijatelnou korozní rychlostí (> 0,01 mm/rok).

Open access
Hydrogen embrittlement of tantalum and tantalum coatings

Zkřehnutí tantalu a tantalových povlaků vodíkem

Z předešlých experimentálních studií vyplývá, že jediným kovovým materiálem s přijatelnou korozní rychlostí v horké koncentrované kyselině fosforečné je tantal. Tento kov může být vhodný jako konstrukční materiál vyvíjených elektrolyzérů vody, pracujících právě s kyselým elektrolytem na bázi kyseliny fosforečné.

Předkládaný článek se zabývá korozním chováním vzorků plnoprůřezového tantalu a povlaků tantalu v prostředí 85 hm. % kyseliny fosforečné za zvýšených teplot (30 °C, 80 °C a 150 °C) zatížených katodickou polarizací. Cílem uvedeného experimentu bylo ověřit vliv vodíkového zkřehnutí povrchu materiálu na jeho celkovou korozní odolnost. Předpokládá se, že vodíkové zkřehnutí tantalu vyvolávají nově formované hydridy v jeho mikrostruktuře. Ve výsledcích předkládaného experimentu byly jednotlivé vzorky podrobeny mechanickým zkouškám tvrdosti podle Vickerse a byla analyzována jejich lomová plocha. Dále byla možná přítomnost hydridů tantalu ověřována prostřednictvím rentgenové difrakční analýzy a množství vodíku v povlaku prostřednictvím GDS-OES. Korozní zkoušky tantalem povlakované korozivzdorné oceli měly odhalit vliv navodíkování na tvorbu defektů povlaků při mechanickém ohybu.

Open access
Effect of the presence of corrosion products on the corrosion rate of lead during the exposition with paper packaging materials

Abstract

High sensitivity of lead to organic compounds leads to degradation of historical lead objects stored in the depositories of museums or archives. High concentration of organic compounds in the atmosphere of depositories is caused by degradation of organic materials (wood, glue, leather, paper). Organic materials are stored together with lead objects or they are used as a packaging material. This study was aimed on the influence of packaging material properties to aggressiveness towards lead with different state of surface by the resistometric method. The results showed that aggressiveness of packaging material is determined by a complex influence of material properties. The presence of corrosion products on the lead surface significantly increases its sensitivity to organic compounds.

Open access
Exposure tests of copper foils in a slurries of different bentonites

Abstract

The goal of the study was to compare corrosion performance of copper in different bentonite slurries. Copper coil samples were exposed in a slurries of bentonites BaM, Rokle, B75, G2M, Voltex, Sabenil. The test was carried out under anaerobic conditions in glovebox at laboratory temperature for duration of one to four months. Samples were evaluated by means of X-ray diffraction and mass loss. Liquid parts of slurries were analysed by ion chromatography and pH meter. The resistance of copper in all studied bentonites was very high. Corrosion rates were in order of tenths of micrometers per year. No trend between pore solution composition and corrosion rate or composition of corrosion products was observed.

Open access
Influence of calcium cations on the corrosion behavior of hot-dip galvanized steel in model concrete pore solutions

Abstract

In this paper, the influence of calcium cations on the corrosion behavior of hot-dip galvanized steel in model concrete pore solutions is evaluated by means of conventional electrochemical methods (measurement of free corosion potencial and polarization resistance), surface analysis methods (optical and confocal microscopy) and XRD phase analysis of precipitated corrosion products. The results of these experiments confirm the conclusions of the current work on a similar topic, i.e. the crystalline calcium based corrosion products Ca[Zn(OH)3]2·2H2O are not able passivate effectively surface of hot-dip galvanized steel in model of concrete pore solutions (pH 12.6; 13.0). If passivation occurs, a mixed Ca[Zn(OH)3]2·2H2O, ZnO and Zn(OH)2 is involved.

Open access
The impact of produced hydrogen gas and calcium zincate on changes of porous structure of cement paste in the vicinity of hot-dip galvanized steel

Abstract

The paper summarizes the impact of produced hydrogen and calcium hydroxyzincate (Ca[Zn(OH)3]2·2H2O) on the formation of the porous structure of cement paste in the vicinity of hot-dip galvanized steel. These substances result from cathodic (hydrogen) and anodic (zincates-formed by reaction with hydroxides) corrosion reactions of hot-dip galvanized steel (or pure zinc) in the cement paste.

The cement binder pore structure was studied by means of mercury porosimetry and analysis of scanning electron microscopy and confocal microscopy images. The porosity of the cement paste at the galvanized steel / cement interphase increased as a result of galvanized steel corrosion while hydrogen was formed. Such a porous structure was maintained throughout the maturation of cement paste. Kinetics of galvanized steel corrosion related primarily to water transport through the binder. The formation of calcium zincate did not result in transition of galvanized steel from active to passive state corrosion.

Open access
Zhodnocení vlivu koroze žárově zinkované oceli na soudržnost hladkých prutů s betonem třídy „NSC“

Článek shrnuje aspekty zkoušení a ovlivňování soudržnosti výztuží s betonem. Úzce se zaměřuje na hodnocení míry vlivu nevyhnutelné koroze povlaku žárového zinku v čerstvém betonu na samotnou soudržnost. Ovlivnění soudržnosti vlivem vývoje vodíku a expanzních korozních produktů zinku je ověřováno na hladkých ocelových prutech. Povlak žárového zinku byl vytvořen konvenční ponorovou technologií. Realizováno bylo normované zkoušení soudržnosti výztuže s betonem na krychlích („vytahovací zkouška“) dle ČSN 73 1328. V závěrech jsou diskutovány i jiné vlivy, které mohou mít dopad na vývoj soudržnosti, především pak vliv obsahu chromanů v použitém cementu a samotná skladba vyloučeného povlaku.

Open access
Corrosion behaviour of steel CSN 422707.9 in concentrated synthetic bentonite pore water

Abstract

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.

Open access
Inhibition efficiency of sodium salts of carboxylic acids on corrosion of lead in archive environment

Abstract

Lead in archive environment suffers from severe corrosion attack caused by the organic acids’ vapours usually presented in such an environment. One of possible ways of corrosion protection of lead is its surface treatment by solutions of sodium salts of monocarboxylic acids (general formula CH3(CH2)n-2COONa, noted NaCn, n = 10, 11, 12). The principle of this corrosion protection is a creation of conversion coating on the lead’s surface, which decreases corrosion rate of lead in the atmospheric environment polluted by organic acids’ vapour. Our research aims at the selection of a suitable protection system that would be applicable to conservation of historical lead in archives and museums. This paper evaluates the corrosion behaviour of treated lead based on the values of polarisation resistance and shape of potentiodynamic curves in simulated corrosive environment (0.01 mol l−1 solution of acetic acid). The lead samples with different state of surface (pure, corroded and electrochemically cleaned) were treated with sodium salts of monocarboxylic acids NaCn (n = 10, 11, 12) having concentration of 0.01 and 0.05 mol l−1. In simulated corrosive atmosphere (above 0.001 mol l−1 acetic acid solution vapours), corrosion rate was measured by means of electrical resistance technique. The inhibition efficiency of monocarboxylic acids is dependent on their carbon chain length and their concentration. The greatest inhibiting efficiency in corrosive atmospheres and for all lead samples was observed for the sodium salt of dodecanoic acid having concentration of 0.05 mol l−1. Artificially created corrosion products and salt coatings were analysed by X-ray diffraction analysis and their surface morphology was observed by scanning electron microscopy. A protective salt coatings are mainly composed of metallic soaps in dimer form.

Open access