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Open access

M. Danková, A. Kalendová and J. Machotová

Abstract

The requirements put on coating materials are more and more stringent mainly in the environmental domain, especially as regards VOC emissions. This is why water-based binders as alternatives to solvent-based binders, to provide paints possessing equally good use properties, are intensively sought. The objective of this work was to assess the anticorrosion and chemical properties of paint films based on new self-cross-linking acrylic latexes. The latexes were synthesized via two--step emulsion polymerisation to obtain a core-shell system. Nanostructural ZnO in an amount of 1.5 wt. % was added to the system during the latex binder synthesis. Paints with an enhanced corrosion resistance and chemical resistance of the films were prepared. The binders prepared were pigmented with anticorrosion pigments and their properties were compared to those of commercial water-based dispersions with either identical or different paint film formation mechanisms. The results gave evidence that if a well-selected pigment is used, the binders can be used to obtain anticorrosion coating materials for metallic substrates.

Open access

A. Guzanová, J. Brezinová, D. Draganovská and P.O. Maruschak

Abstract

The paper focuses on assessment the resistance of hot-sprayed coatings applied by HVOF technology (WC–Co–Cr created using powder of two different grain sizes) against erosive wear by dry-pot wear test in a pin mill at two sample angles. As these coatings are designated for the environment with varying elevated temperatures and often are in contact with the abrasive, the coatings have been subjected to thermal cyclic loading and their erosive resistance has been determined in as-sprayed condition and after the 5th and 10th thermal cycles. The corrosion resistance of coatings was evaluated by linear polarization (Tafel analysis).

Open access

Prasad U. Syam, V. V. Kondaiah, K. Akhil, V. Vijay Kumar, B. Nagamani, K. Jhansi, Ravikumar Dumpala, B. Venkateswarlu and Sunil B. Ratna

Abstract

Magnesium and its alloys are now attracting a great attention as promising materials for several light weight engineering applications. ZE41 is a new Mg alloy contains Zinc, Zirconium and Rare Earth elements as the important alloying elements and is widely used in aerospace applications. In the present study, heat treatment has been carried out at two different temperatures (300 and 335 °C) to assess the effect of heat treatment on microstructure and corrosion behavior of ZE41 Mg alloy. The grain size was observed as almost similar for the unprocessed and heat treated samples. Decreased amount of secondary phase (MgZn2) was observed after heat treating at 300 °C and increased intermetallic phase (Mg7Zn3) and higher number of twins appeared for the samples heat treated at 335 °C. Microhardness measurements showed increased hardness after heat treating at 300 °C and decreased hardness after heat treating at 335 °C which can be attributed to the presence of higher supersaturated grains after heat treating at 300 °C. The samples heat treated at 335 °C exhibited better corrosion resistance compared to those of base materials and samples heat treated at 300 °C. From the results, it can be understood that the selection of heat treatment temperature is crucial that depends on the requirement i.e. to improve the microhardness or at the loss of microhardness to improve the corrosion resistance of ZE41 Mg alloy.

Open access

D. Kajánek, B. Hadzima, J. Tkacz, J. Pastorková, M. Jacková and J. Wasserbauer

Abstract

The coating prepared by plasma electrolytic oxidation (PEO) was created on AZ31 magnesium alloy surface with the aim to evaluate its effect on corrosion resistance. The DC current was applied on the sample in solution consisted of 10 g/l Na3PO4·12H2O and 1 g/l KOH. Additional samples were prepared with 2 and 4 minutes of preparation to observe evolution of the PEO coating. Morphology of the coatings was evaluated by scanning electron microscopy and chemical composition was examined by EDX analysis. Electrochemical characteristic were measured by potentiodynamic polarization tests and electrochemical impedance spectroscopy in 0.1 M NaCl at the laboratory temperature. Obtained data were presented in form of potentiodynamic curves and Nyquist diagrams. Results of analysis showed that plasma electrolytic oxidation coating positively influence corrosion resistance of AZ31 magnesium alloy in chosen corrosive environment.

Open access

J. Fojt, V. Hybasek, P. Jarolimova, E. Pruchova, L. Joska and J. Malek

Abstract

The titanium bioactivity could be increased by surface nanostructuring. Titanium alloys are using for dental implants manufacturing. It represents a specific problem because of using of the dental treatments with high concentration of fluoride ions and with acidic pH. The corrosion resistance of nanostructured surface of titanium beta alloy in environments with fluoride ions was examined by common electrochemical technique. The electrochemical impedance measurement showed high corrosion resistance in physiological solution. The fluoride ions have expected negative influence on corrosion behaviour of the layer. The nanotube bottom was preferentially attacked which resulted in layer undercoroding and its detachment.

Open access

H. Geiplová, L. Mindoš, J. Mrázek, D. Majtás, P. Macová and P. Pokorný

Abstract

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.

Open access

P. Pokorný, M. Hrabánek and H. Geiplová

Abstract

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.

Open access

K. C. Strachotová, M. Kouřil, K. Kuchťáková and Š. Msallamová

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

P. Pokorný and M. Kouřil

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

J. Stoulil, M. Kouřil and D. Dobrev

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.