Journal KOM

Research Articles

Korózne charakteristiky spekaných heterogénnych materiálov pozostávajúcich zo železa a jeho oxidov / Corrosion characteristics of sintered heterogeneous materials composed of iron and iron oxides
Kupková M., Kupka M., Oriňaková R., Gorejová R.
2020, 64 (3), 72–78

Citace (ACS): Kupková, M.; Kupka, M.; Oriňaková, R.; Gorejová, R. Korózne charakteristiky spekaných heterogénnych materiálov pozostávajúcich zo železa a jeho oxidov / Corrosion characteristics of sintered heterogeneous materials composed of iron and iron oxides. Koroze a ochrana materiálů 2020, 64 (3), 72–78.

Citace (ISO): Kupková, M.; Kupka, M.; Oriňaková, R.; Gorejová, R. Korózne charakteristiky spekaných heterogénnych materiálov pozostávajúcich zo železa a jeho oxidov / Corrosion characteristics of sintered heterogeneous materials composed of iron and iron oxides. Koroze a ochrana materiálů 2020, vol. 64, no. 3, p. 72–78.

Pri koronárnej angioplastike či v ortopedickej chirurgii sa často používajú kovové implantáty poskytujúce mechanickú oporu liečeným tkanivám. V niektorých situáciách je táto opora potrebná len dočasne. Po skončení liečby už implantát neprináša žiadny úžitok a jeho prítomnosť môže časom spustiť nežiaduce reakcie. Optimálnym riešením by mohli byť krátkodobé implantáty ktoré sa po čase v tele rozložia a produkty rozkladu telo ľahko vylúči. Železo, jeho zliatiny a zlúčeniny sú potenciálne materiály pre biodegradovateľné zariadenia. Pre úspešnú aplikáciu konkrétneho materiálu je však potrebné vedieť a môcť regulovať rýchlosť jeho korózie. V tomto príspevku sa študuje korózia kompozitov zložených zo železa a oxidov železa. Aby sa takýto materiál získal, granule z oxidov železa sa čiastočne redukovali, zlisovali a spekali. Výsledkom boli materiály pozostávajúce zo železa a oxidov železa. Pripravili sa vzorky zo spekaných materiálov a z materiálov po spekaní ešte raz redukovaných. Testovanie metódou potenciodynamickej polarizácie v Hanksovom roztoku naznačuje, že korózia vzoriek je galvanická, pričom uvoľňovanie dvojmocných iónov železa z povrchu železa predstavuje anódovú reakciu a redukcia rozpusteného kyslíka prebiehajúca na povrchu železa a oxidov železa predstavuje katódovú reakciu. Zmeny v obsahu oxidov železa vo vzorke predpokladaným spôsobom posúvali korózny potenciál a zdanlivú koróznu prúdovú hustotu.

In a coronary angioplasty or orthopaedic surgery, metallic implants are often used to provide mechanical support to the healing tissues. In some situations, this support is really needed only temporarily. After tissue recovery, the implant no longer provides any benefits and can trigger adverse reactions. An optimal solution might be the short-term implants which are able to decompose in situ and can be readily excreted from the body. Iron-based materials are promising candidates for application in biodegradable devices. For the successful application, the ability to control the material's corrosion rate is important. In this contribution, the corrosion of iron-iron oxide composites is investigated. In order to obtain such materials, iron-oxide granules were incompletely reduced, compacted and sintered. Materials consisting of a pure iron and iron oxides were obtained. Specimens from as-sintered materials and materials reduced once again after sintering were prepared. Potentiodynamic polarization testing in Hanks' solution indicated that specimens underwent a galvanic corrosion, where the release of ferrous ions from iron surfaces represents the anodic reaction and the oxygen reduction on surfaces of both iron and iron oxides represents the cathodic reaction. Changes in the content of oxides resulted in anticipated shifts in corrosion potential and apparent corrosion current density.

Technology and developement

Use of ultrasound for cleaning of components of historical vehicles in Technical Museum in Brno
Rapouch K., Mrázek M.
2020, 64 (3), 79–86

Citace (ACS): Rapouch, K.; Mrázek, M. Use of ultrasound for cleaning of components of historical vehicles in Technical Museum in Brno. Koroze a ochrana materiálů 2020, 64 (3), 79–86.

Citace (ISO): Rapouch, K.; Mrázek, M. Use of ultrasound for cleaning of components of historical vehicles in Technical Museum in Brno. Koroze a ochrana materiálů 2020, vol. 64, no. 3, p. 79–86.

In the collections of Technical Museum in Brno, large number of historical vehicles is placed. During the operation, parts of their motors are being fouled. Frequently, they become even immobile (e. g. due to a fouled fuel system). In this case, the method using ultrasound with a suitable concentrate appears as the most suitable. In fact, ultrasound works also in inaccessible places with large efficiency. Not only the chosen solution influences the cleaning efficiency, but also parameters as time, bath temperature and ultrasound frequency. The cleaning process was evaluated according to the volume of removed dirt and by observing wettability change using the measuring of contact angle of a water drop. The ultrasound shock waves influence the surface to a certain extent also mechanically. That is why, the ultrasound effect on defects in the structure was observed. The aggressivity of cleaning concentrates was evaluated on the ground of determination of dissolved metals in the baths by ET AAS method.

Long-term outdoor exposure of artificial copper patina based on brochantite
Bureš R., Rak P., Stoulil J.
2020, 64 (3), 87–94

Citace (ACS): Bureš, R.; Rak, P.; Stoulil, J. Long-term outdoor exposure of artificial copper patina based on brochantite. Koroze a ochrana materiálů 2020, 64 (3), 87–94.

Citace (ISO): Bureš, R.; Rak, P.; Stoulil, J. Long-term outdoor exposure of artificial copper patina based on brochantite. Koroze a ochrana materiálů 2020, vol. 64, no. 3, p. 87–94.

A typical green layer of patina starts to cover copper in atmosphere condition, which is aesthetically acceptable and also provides protective properties. This work investigates stability of the artificial patina layer based on sulphates prepared from a gaseous phase during two-year exposure in atmosphere condition. XRD and SEM were employed to verify the composition and morphology of artificial patina. Colour and patina coverage were compared before and after exposure also. According to results after 1 and 2 years of exposure, it is possible to see changing of hydroxyl sulphates to more stable brochantite and filling pores in the patina layer. There is almost no colour change, however lower patina coverage is slightly evident due to precipitation and abrasive effect.

Testing of pilot 2 m3 exposure chamber for formation of brochantite based patina on copper and copper alloys – objects of practical dimensions
Bureš R., Rak P., Stoulil J.
2020, 64 (3), 95–99

Citace (ACS): Bureš, R.; Rak, P.; Stoulil, J. Testing of pilot 2 m3 exposure chamber for formation of brochantite based patina on copper and copper alloys – objects of practical dimensions. Koroze a ochrana materiálů 2020, 64 (3), 95–99.

Citace (ISO): Bureš, R.; Rak, P.; Stoulil, J. Testing of pilot 2 m3 exposure chamber for formation of brochantite based patina on copper and copper alloys – objects of practical dimensions. Koroze a ochrana materiálů 2020, vol. 64, no. 3, p. 95–99.

Formation of natural patina on copper and copper alloys objects takes tens of years. There are solutions for patination, which are used in restorers’ practice. However, these artificial patinas are usually based on nitrates, carbonates or chlorides. Patina based on brochantite is the most stable phase under atmospheric conditions. This type of patina was successfully formed in laboratory in a small exposure chamber with higher content of SO2. This work is next step of the experiment to make this method become more practicable. It started with construction 2 m3 exposure chamber and simulation of ideal conditions for patination process. The length of drying phase, homogeneity of conditions, pH of feeding water, colour of patina, placement of samples and final appearance were observed. The chamber construction allows to achieve ideal pH value of feeding water, samples surface became dry during the ventilation and temperature during condensation was stable at 40 °C. These conditions are ideal for patination process.

Reviews

Metody zvýšení odolnosti papírenských produktů proti hoření / Methods of increasing the fire resistance of paper products
Nováková M., Ďurovič M.
2020, 64 (3), 100–107

Citace (ACS): Nováková, M.; Ďurovič, M. Metody zvýšení odolnosti papírenských produktů proti hoření / Methods of increasing the fire resistance of paper products. Koroze a ochrana materiálů 2020, 64 (3), 100–107.

Citace (ISO): Nováková, M.; Ďurovič, M. Metody zvýšení odolnosti papírenských produktů proti hoření / Methods of increasing the fire resistance of paper products. Koroze a ochrana materiálů 2020, vol. 64, no. 3, p. 100–107.

Rešerše pojednává o možnostech zvýšení požární odolnosti papíru, kartonu či lepenky. Zahrnuje principy retardace hoření i požadavky na vhodný přípravek. Uvádí příklady látek a směsí, které se podle odborné literatury používají či používaly při výrobě nebo dodatečném ošetřování papírenských výrobků. Článek je též průběžně doplněn příklady z patentové literatury.