D. Steinerová, A. Kalendová, J. Machotová and M. Kohl
Water based paints are increasingly attracting interest mainly with a view to reducing air pollution with volatile organic compounds (VOC). However, the protective properties of water-based paints are inferior to those of solvent-based paints and so new ways to increase the resistance of water-based systems are sought. The present contribution describes the preparation and testing of environmentally friendly anti-corrosion paints based on novel water-based self-crosslinking acrylate latexes containing appropriate pigments and ZnO or MgO nanoparticles at a concentration of 1.5 % (with respect to the monomers) compared to the same systems free from the nanoparticles. Both the effect of the MeO nanoparticles and the effects of the pigment species and particle shapes on the paint film properties were examined. The MeO nanoparticles were found to improve all the properties tested. The latexes with MgO exhibited the highest resistance to flash corrosion while the latexes with ZnO exhibited the highest anticorrosion resistance. Furthermore, the systems with the calcium-aluminium polyphosphosilicate based pigment were superior to all the remaining systems in this respect. It is concluded that binders with nanoparticles can be used as a basis for anticorrosion coatings provided that a suitable pigment is selected.
J. Brezinová, A. Guzanová, D. Draganovská and J. Brezina
The paper presents results of the research focused on the characterization of two types of coatings – WC–FeCrAl and WC–WB–Co. The properties of the WC–FeCrAl coating (Co and Ni free) were compared against the WC–WB–Co coating to see if it could be used as an environmentally more suitable substitute for conventional Co and Ni containing powders. The coatings were applied by HVOF technology. The influence of thermal cyclic stress on the hardness, adhesion of coatings and their corrosion resistance was determined. A change in the phase composition of coatings after thermal cyclic loading was also determined.
J. Drábiková, S. Fintová, P. Doležal, J. Wasserbauer and Z. Florková
Magnesium based alloys are very promising material to be used mainly for biodegradable implants in medical applications. However, due to their very low corrosion resistance in the environment of in vivo is their use limited. Increase of the corrosion resistance of magnesium alloys in vivo can be achieved, for example, by a suitable choice of surface treatment while the biocompatibility must be ensured. Fluoride conversion coatings meet these requirements. Unconventional fluoride conversion coating was prepared on ZE41 magnesium alloy by dipping the magnesium alloy into the Na[BF4] salt melt at 450 °C for 0.5; 2 and 8 h. The morphology and thickness of the prepared fluoride conversion coatings were investigated as well as the corrosion resistance of the treated and untreated ZE41 magnesium alloy specimens. The corrosion resistance of the untreated and treated ZE41 magnesium alloy was investigated using electrochemical impedance spectroscopy in the environment of the simulated body fluids at 37 ± 2 °C. The obtained results showed a positive influence of the fluoride conversion coating on the corrosion resistance of the ZE41 magnesium alloy.
J. Tkáčová, E. Zdravecká, E. Evin, M. Tomáš and D. Jakubéczyová
For achieving a long service life of stamping dies for new types of steel sheets intended for the automotive industry, the tribosystem must be optimally designed. One of the possible solutions is its optimization by coatings. More modern coating technologies for stamping dies include PVD (physical vapor deposition) and CVD (chemical vapor deposition) methods. The properties of PVD TiCN and DLC (diamond-like carbon) coatings deposited on ledeburitic high-alloy Cr–Mo–V steel were analyzed by standard tests (coating adhesion by both the scratch and Rockwell C tests, microhardness by Vickers method and coating thickness by Calotest) and developed tribo-meter of the “friction jaw-roller” type at drawing double-sided hot-dip galvanized steel sheet. The obtained results showed better tribological behavior of the DLC coating.
Corrosion flaws in pipelines can caused severe financial losses and also can be dangerous for people. One of the most frequently damaged parts are dissimilar pipe welds. We would like to understand how corrosion process reacts on corrosion product removal. Outputs from experiment will be used for production of test specimens. For testing we chose standard dissimilar weldment used in Czech power plants. It is joint with 08Ch18N10T and 22K (GOST) steel. Joint is cut to 24 same specimens. There are exposed to flowing water solution of 5% NaCl. Half of the specimens are regularly mechanically cleaned. The joint is metallographically observed and parts with and without corrosion products are compared. Water salt solution increased pH from 7,25 to 7,86 during 31 days test and conductivity varies around 74 mS cm−1. Metallographic observation indicates that corrosion under corrosion products layer is locally speed up and causes pitting corrosion. Cleaned specimens indicate plane corrosion with lower depth. These results indicate that slag in pipeline could locally speed up corrosion depth penetration. On the other hand, solutions with abrasive particles (which can wipe out the corrosion product) will probably facilitate plane corrosion damage on pipeline walls. This test brings us another knowledge, how to simulate realistic corrosion damage for production of NDT qualification test pieces.
Ethanol produced from renewable resources is considered as an ecological substitute for a fossil gasoline. Ethanol blended with the fossil gasoline is able to significantly change the properties of the blended fuel as polarity, conductivity, ability to absorb air humidity and ability to dissolve a high percentage of water etc. All these properties are growing with an increasing content of ethanol and all of them can cause higher corrosivity of blended fuel. Material compatibility of metalic construction materials of the vehicle fuel system is also decreased in the environment of ethanol – gasoline blends (EGB’s). Furthermore, components of production, transport and storage equipment may be at risk of corrosion. EGB’s with an ethanol content of about 60% vol. show high corrosive aggressivness, especially if they are contaminated with water and trace amounts of ion, which may occur if proper storage, transport and production conditions are violated. Losses caused by corrosion of equipment may be prevented by using of suitable additive. Diethylenetriamine (DETA) can be used as such additive for the mild steel which is one of the most commonly used construction material. When DETA is used, it shows very high efficiency.
L. Poberezhny, A. Stanetsky, G. Grytsuliak, L. Poberezhna, M. Kosmii and A. Hrytsanchuk
The study of the deformation behavior of the pipeline material in conditions of loads and influences simulating the operation allows better estimation of the residual life of the pipelines and more accurate forecasting of the operating costs. The kinetics of deformation in 6 model environments simulating soil electrolytes was studied. Corrosion-mechanical tests were performed and the impact of the soil electrolyte chemical composition and the applied mechanical stresses on the corrosion behavior of the pipeline steel was studied. Significant increase in the corrosion activity of the soil electrolyte due to the synergistic effect of the corrosion-active components was found in the specified ratios of the ionic molar concentrations of sulphate and chloride ions (0.05 M: 0.1 M).
The oxidation kinetics of depleted uranium and its low-alloy molybdenum alloys (U-2wt.%Mo, U-5wt.%Mo) were measured in a moist air (75% relative humidity) at 60 and 75 ° C. Coefficients of reaction rate equations were determined for linear oxidation kinetics. In the oxidation of depleted uranium at 75 ° C, a change in reaction kinetics from linear to exponential behaviour was observed after about 2500 hours.
R. Gorejová, R. Oriňaková, A. Oriňak, M. Kupková, M. Hrubovčáková and M. Baláž
Biodegradable metallic implants are materials that serve as a temporary implants and scaffolds. They degrade directly in vivo and therefore eliminate need for secondary surgical intervention. They are often made of metals such as magnesium, iron, zinc and can be modified by coating with the inorganic or polymeric layer. In this work iron-based biomaterial was prepared and modified with polymeric (polyethyleneimine, PEI) layer. Its degradation behavior was studied under conditions of simulated body fluids at 37 ± 0.2 °C in the form of static immersion tests. It has been shown that the surface modification caused an acceleration of degradation of the material and also had an influence on the corrosion mechanism.
The beginning of the use of polyester resins for artistic work date back to the late 1950s. Initially, resins were supposed to temporarily replace and imitate traditional but more expensive sculptural materials (stone, bronze). Later, original, especially fiberglass works were created, where the laminate formed a shell connected to the internal supporting steel structure. Until now, only part of the exterior works of art made of polyester resins have been survived. Although polyester resins are considered to have good weather resistance, most exterior sculptures exhibit more or less severe defects, often resulting from neglected maintenance. The main types of defects occurring in polyester fiberglass works are presented. The most serious damage is cracks in the entire thickness of the shell, because water can easily penetrate to the internal steel structure. In the case of prolonged water penetration, the statue may collapse due to corrosion. The article presents the procedure of exploring the fiberglass sculpture from the 1950s with the introduction of suitable methods for the documentation of the state of the work. Finally, suitable restoration interventions to maximize the life of the statues are discussed.