Tom 63 (2019): Zeszyt 1 (March 2019)

This article presents the results of the corrosion survey of the load-bearing structure of the main hall of the Main railway station in Prague. The chemical composition and microscopy view of the metal alloy has been explored, the current state of the anti-corrosion protection system as well as its composition were also evaluated. The corrosion damage of sheets and reinforcements of individual columns of the peron hall is also reported. The corrosion damage of the plates and reinforcements is locally very significant and is related to the drainage of rain water from the damaged roof structure. Renovation is also necessary for the protective coating system. The article concludes a restoration project that fully respects the historical form of the construction of the early twentieth century with minimal compromise.

The paper follows the paper describing the condition of wrought iron structure of main railway station [1]. In this paper the investigation of condition of paint system corrosion surface treatment is given and the restoration procedure is described. The withdrawal samples of paint systems were analysed by stratigraphy, FTIR and XRF analysis. Due to identification of Pb pigment presence in primer the water jet technology was chosen which minimalised the danger waste formation.

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.

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.

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 NaC_n, 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 NaC_n (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.

Electrochemical chloride extraction from a reinforced concrete structure may be accompanied with an electrochemical injection of healing agents if such agents are positively charged and are able to migrate towards the activated reinforcement. Positive charge carried by nanoparticles or cathionic corrosion inhibitors might be the proper choice. Organic substances with a positive charge and their salts are mostly such inhibitors. The essential conditions for successful application of such corrosion inhibitors are their sufficient corrosion inhibition efficiency that was studied and evaluated and their stability of positive charge in chloride containing concrete pore solution.

The corrosion survey of the supporting steel/cast iron structure of the palm greenhouse included not only the characteristics of the used metal materials (microstructure, chemical composition), but also the current state of the system of corrosion protection (thickness and stratigraphy of the applied coating system). From a static point of view, the palm greenhouse design meets the applicable standards if two damaged cast iron columns are repaired. A new top coat with extended corrosion resistance is required on the surface of individual metal profiles.