Časopis KOM

Výzkumné články

Corrosion resistance of AZ31 magnesium alloy treated by plasma electrolytic oxidation

Kajánek D., Hadzima B., Tkacz J., Pastorková J., Jacková M., Wasserbauer J.
2019, 63 (2), 65–71

Citace (ACS): Kajánek, D.; Hadzima, B.; Tkacz, J.; Pastorková, J.; Jacková, M.; Wasserbauer, J. Corrosion resistance of AZ31 magnesium alloy treated by plasma electrolytic oxidation. Koroze a ochrana materiálů 2019, 63 (2), 65–71.

Citace (ISO): Kajánek, D.; Hadzima, B.; Tkacz, J.; Pastorková, J.; Jacková, M.; Wasserbauer, J. Corrosion resistance of AZ31 magnesium alloy treated by plasma electrolytic oxidation. Koroze a ochrana materiálů 2019, vol. 63, no. 2, p. 65–71.

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.

Na povrchu horčíkovej zliatiny AZ31 bola pomocou plazmovej elektrolytickej oxidácie (PEO) pripravená vrstva s cieľom hodnotenia jej vplyvu na koróznu odolnosť. Na vzorku bol aplikovaný jednosmerný prúd v roztoku zloženom z 10 g/l Na3PO4·12H2O a 1 g/l KOH. Z dôvodu sledovania vývoja vrstvy boli pripravené aj vzorky s časom prípravy 2 a 4 minúty. Morfológia vrstiev bola hodnotená skenovacou elektrónovou mikroskopiou a ich chemické zloženie bolo hodnotené EDX analýzou. Vplyv PEO vrstvy na elektrochemické charakteristiky bol hodnotený pomocou potenciodynamických skúšok a elektrochemickej impedančnej spektroskopie v roztoku 0,1 M NaCl pri laboratórnej teplote. Získané dáta boli prezentované vo forme potenciodynamických kriviek a Nyquistových diagramov. Z výsledkov analýz vyplýva, že PEO vrstva priaznivo ovplyvňuje koróznu odolnosť horčíkovej zliatiny AZ31 vo zvolenom koróznom prostredí. 

Výzkumné články

Corrosion behaviour of the titanium beta alloy nanotubular surface in the presence of fluoride ions

Fojt J., Hybasek V., Jarolimova P., Pruchova E., Joska L., Malek J.
2019, 63 (2), 72–78

Citace (ACS): Fojt, J.; Hybasek, V.; Jarolimova, P.; Pruchova, E.; Joska, L.; Malek, J. Corrosion behaviour of the titanium beta alloy nanotubular surface in the presence of fluoride ions . Koroze a ochrana materiálů 2019, 63 (2), 72–78.

Citace (ISO): Fojt, J.; Hybasek, V.; Jarolimova, P.; Pruchova, E.; Joska, L.; Malek, J. Corrosion behaviour of the titanium beta alloy nanotubular surface in the presence of fluoride ions . Koroze a ochrana materiálů 2019, vol. 63, no. 2, p. 72–78.

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. 

Výzkumné články

Effect of heat treatment on microstructure, microhardness and corrosion resistance of ZE41 Mg alloy

Syam Prasad U., Kondaiah V. V., Akhil K., Vijay Kumar V., Nagamani B., Jhansi K., Ravikumar Dumpala, Venkateswarlu B., Ratna Sunil B.
2019, 63 (2), 79–85

Citace (ACS): Syam, P.; Kondaiah, V.; Akhil, K.; Vijay, K.; Nagamani, B.; Jhansi, K.; Ravikumar, D.; Venkateswarlu, B.; Ratna, S. Effect of heat treatment on microstructure, microhardness and corrosion resistance of ZE41 Mg alloy . Koroze a ochrana materiálů 2019, 63 (2), 79–85.

Citace (ISO): Syam, P.; Kondaiah, V.; Akhil, K.; Vijay, K.; Nagamani, B.; Jhansi, K.; Ravikumar, D.; Venkateswarlu, B.; Ratna, S. Effect of heat treatment on microstructure, microhardness and corrosion resistance of ZE41 Mg alloy . Koroze a ochrana materiálů 2019, vol. 63, no. 2, p. 79–85.

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.

Výzkumné články

Properties of coatings created by HVOF technology using micro- and nano-sized powder

Guzanová A., Brezinová J., Draganovská D., Maruschak P.O.
2019, 63 (2), 86–93

Citace (ACS): Guzanová, A.; Brezinová, J.; Draganovská, D.; Maruschak, P. Properties of coatings created by HVOF technology using micro- and nano-sized powder . Koroze a ochrana materiálů 2019, 63 (2), 86–93.

Citace (ISO): Guzanová, A.; Brezinová, J.; Draganovská, D.; Maruschak, P. Properties of coatings created by HVOF technology using micro- and nano-sized powder . Koroze a ochrana materiálů 2019, vol. 63, no. 2, p. 86–93.

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). 

Výzkumné články

Self-crosslinking acrylic latexes containing nanoparticles ZnO with increased corrosion and chemical resistance of coating

Danková M., Kalendová A., Machotová J.
2019, 63 (2), 94–99

Citace (ACS): Danková, M.; Kalendová, A.; Machotová, J. Self-crosslinking acrylic latexes containing nanoparticles ZnO with increased corrosion and chemical resistance of coating . Koroze a ochrana materiálů 2019, 63 (2), 94–99.

Citace (ISO): Danková, M.; Kalendová, A.; Machotová, J. Self-crosslinking acrylic latexes containing nanoparticles ZnO with increased corrosion and chemical resistance of coating . Koroze a ochrana materiálů 2019, vol. 63, no. 2, p. 94–99.

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-crosslinking 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.