In this paper, tests of some physico-chemical properties of protective epoxy coating on non-alloy structural steel grade type S235JRG2 have been carried out. This is a significant construction ...material whose use is remarkably important for many steel products such as H beam, I beam, transmission towers, steel pipe etc. Coatings represent one of the ways to protect metal from corrosion. The properties of coating thickness, hardness, gloss, and adhesion were investigated. The same properties were tested by exposing the sample non-alloy steel plates to corrosive conditions of the salt and humid chamber and seawater. Part of the samples prior to application of the coating were immersed to phosphate solution to further investigate the effects of phosphatization on the properties of the coating. After exposure of the plates to the humidity chamber conditions, no traces of corrosion products, cracking or peeling of the coating were found on the surfaces. The plates tested in the sea water and salt chamber showed a minor damage on protective coating. The traitability properties were tested by the Pull off Adhesion test. Force pull adhesion off test shows less value for unphosphated samples than for phosphated ones.
The purpose of this research is to investigate the influence of the phosphatizing process with Ni2+, Ce3+, and Ti2+ ions on the properties of the coating to obtain better corrosion protection of the ...metal. Steel corrosion occurs through physicochemical interaction between the metal and its surrounding environment. This leads to a change in the metal’s physical, mechanical, and optical properties that can cause damage to the functionality of the metal, which in turn may result in accidents or other malfunctions. Carbon steel grade has limited resistance to corrosion, depending on the carbon content and alloying element, the microstructure, and the surrounding environment of the material. This paper present tests that have been carried out on some of the physicochemical properties of protective epoxy and polyurethane coating on carbon steel grade. Coatings represent one of the methods available to protect metal surfaces from corrosion. Coating properties such as thickness, hardness, and adhesion were investigated. The same properties were tested by exposing the sample plates to corrosive conditions of the humid chamber and seawater. Their anticorrosion properties were explored by electrochemical impedance spectroscopy (EIS) techniques under immersion in 3.5 wt.% NaCl solutions as a corrosive medium. Part of the samples prior to application of the coatingwere modified with a phosphate solution containing metal ions: Ni2+, Ce3+, and Ti2+ to further investigate the effects of phosphatization on the properties of the coating. After exposure of the plates to the salt and moist chamber conditions, no traces of corrosion products, cracking or peeling of the coating were found on the surfaces. The adhesion properties were tested by the pull-off adhesion test. It was found that metal/polymer adhesion was satisfied according to EN ISO 4624:2016 and had the same value for all samples. However, a detailed EIS analysis showed a higher resistance of phosphate samples with Ce3+ ions than samples that were phosphated with Ni2+ and Ti2+ ions and those that did not have a sparingly soluble phosphate salt layer.
Radon is known as the main contributor to natural background radiation exposure and the mapping of different radon phenomenon presents an important task in both a scientific and regulatory context. ...Considering the aspect of radon effects on health, identification of areas with elevated radon levels is a crucial step in radon monitoring and the prevention of adverse effects on the population and the environment. Different needs regarding the monitoring of the environmental radioactivity levels in Europe led to initiatives such as the development of the European Atlas of Natural Radiation (EANR). To present different methods of radon mapping, the European Indoor Radon Map and European Geogenic Radon Map projects are described briefly. The aim of this paper is to present the mapping of different aspects of radon (indoor and geogenic) and its importance in data visualization and information dissemination. The practical experiences worldwide provide context for future activities of radon mapping in Croatia. Existing Croatian initiatives in the field of radon risk research are mostly related to the investigations of indoor radon concentrations and identification of radon prone areas through one national study and several focused studies. A comparison of indoor radon levels in Croatia and several geological parameters identified new areas appropriate for future research that could lead towards a geogenic map of radon potential in Croatia.
In one part of the groundwater flow in the Vrelić cave (near the village Donje Dubrave), during the explorations in 2003, oil pollution was perceived. During field prospection and contact with local ...population, few possible pollution sources were located. There was a strong possibility that the oil traces in the cave are the result of the railway accident in 1970. Because of the railway accident on Rijeka-Zagreb railroad, tank carriage sliped off from the tracks and the content of the dangerous cargo leaked onto the nearby valley, 800 meters away from the cave entrance. A spring, used sometimes for water supply by the local population is also located nearby. Sampling of the water from the cave and the spring was carried out several times during the next period with the intention of monitoring the pollution impact on water quality in different seasonal (climatic) conditions. In the course of the laboratory analysis of the samples the following parameters were determined: Total hardness; Concentrations of Calcium, Magnesium, Iron, Chlorides and Nitrates; pH-value; TOC; colony-forming unit (CFU); total Coliform; fecal Streptococus; Proteus bacteria; Salmonella bacteria and Clostridium perfringens bacteria. Several of other parameters were also measured by mobile devices: Conductivity (EC), TDS, Redox-potential, pH-value and water temperature. Water tracing with Na-fluorescine was carried out before the analysis and the connection between groundwater flow in cave and the spring water was confirmed. After the creation of a topographical (speleological) map of the cave and thanks to the surface (field) measurements, the distance between the place of Na-fluorescine spill in the cave and the Vrelić spring was defined (the paper is published in Croatian).
In the present study corrosion inhibition of carbon steel in CO2-saturated chloride–carbonate solution by the olive leaf extract has been researched. For that purpose the electrochemical and ...spectrophotometric techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy and Fourier transform infrared spectroscopy were employed. Both electrochemical techniques, potentiodynamic polarization and electrochemical impedance spectroscopy, demonstrate that olive leaf extract inhibits the carbon steel corrosion in CO2-saturated chloride–carbonate solution. It was determined that the inhibition efficiency increases with increasing concentration of the olive leaf extract. The olive leaf extract achieves high corrosion efficiency as a mixed type inhibitor, with a prevailing influence on the anode process. Recorded electrochemical impedance spectra in the presence of the extract show the presence of the inhibitor film on the steel surface. This is further confirmed by the recording in Fourier transform infrared spectroscopy spectrum.
Geochemical environment can influence human health causing chronic medical problems related to long-term, low-level exposures to toxic agents such are trace elements. Humans can be directly exposed ...to toxic substances by inhalation of air dust or indirectly through food chain or by consumption of local water for drinking, cooking, personal hygiene and recreational purposes. Chronic medical problems related to geochemical characteristics of the environment can also be caused by chronic deficit of chemical elements essential for humans. In this paper we will present several applications of the GIS and statistical methods for relating the geographical distribution of diseases with geochemical characteristics of the environment. In addition, we are presenting methods applied for distinguishing natural distribution of elements from anthropogenic contribution, which is important information for establishing protective measures necessary for decreasing the health risk (the paper is published in Croatian).
Protective coatings are the most widely used corrosion protection method for construction materials in different environmental conditions. They isolate metals from aggressive media, making the ...structure more durable. Today, alongside good anti-corrosive properties, coatings need to be safe for the environment and harmless to those who apply them. The high volatile organic compound (VOC) content in conventional solvent-borne coatings presents a huge ecological problem. A solution for indispensable solvent emission reduction is the application of powder coatings. This study evaluates the corrosion performance and surface morphology of polyester and epoxy–polyester powder coatings. Electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) measurement, salt spray chamber and humidity chamber testing followed by adhesion testing were used to investigate the protective properties of powder coatings. Scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX) was used to analyse the surface morphology and chemical composition, whereas the microstructure and coating uniformity were determined by optical microscope examination. The research revealed a negative influence of coating surface texture on coating thickness and consequently a lack of barrier and adhesion properties. The epoxy–polyester powder coating showed a better performance than the polyester coating. All tested coatings showed uniform structure.
Cathodic disbonding of the underwater-applied, ultra-thick, solvent free epoxy coating subjected to various levels of cathodic protection was investigated during the period of the coating cure. The ...results indicate that the partially cured coating was of low resistivity, between 10
3 and 10
5
Ω
cm
2 for the cathodic polarization of on-potentials between −0.98 and −1.4
V
Ag/AgCl/sw. The coating was shown to be capable of withstanding normal levels of cathodic protection between off-potentials of −0.8 and −1.1
V
Ag/AgCl/sw while the IR drop, introduced by the coating in the same potential range, increased from 0.06 to 0.1
V and has to be taken into account at the design stage of the cathodic protection system. Beneficial influence of calcareous deposit formation on the cathodic protection current was confirmed, particularly for the failed coating. The initial period (1
week) of coating cure was shown as the most critical for disbonding processes caused by the excessive cathodic polarization.
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