opk Current issue
Corrosion of electrodeposited nickel with graphene oxide and its effect on hydrogen evolution in water electrolysis
Uniwersytet im. Kardynała Stefana Wyszyńskiego (UKSW), Warszawa
Instytut Chemii Fizycznej PAN, Warszawa
Large scale production of hydrogen by water electrolysis needs effective electrodes made from cheap earth - abundant materials. Widely used are nickel electrodes whose effectiveness can be improved by carbon materials, including graphene and graphene oxide (GO). In this work, electrodeposits of nickel (Ni) and of nickel with GO (Ni/GO) were obtained from the Watts solution without and with GO, respectively. Ni deposits were flat, whereas Ni/GO deposits had cauliflower morphology with developed surface area. Electrochemical behaviour was examined in 0.1 M Na2SO4 . In comparison with Ni, Ni/GO showed higher corrosion rate, higher anodic polarization currents, and higher cathodic hydrogen evolution reaction (HER). Voltammetric cycling to potentials of passivation caused a rise in HER for both materials, but for Ni/GO it was significantly higher. Enhanced HER on Ni/GO was explained mainly by the formation of larger amounts of catalytically active Ni oxides/hydroxides.
Keywords: Nickel, Graphene oxide, Hydrogen evolution, Anodic oxidation, Electrocatalysis
2019, Vol. 62, nr 7, pp. 220-224
Corrosion of the chromium-nickel steel screenings and grit separator
Wrocław University of Environmental and Life Sciences, Institute of Environmental Engineering
Łukasiewicz Research Network - Electrotechnical Institute, Division of Electrotechnology and Materials Science
Austenitic chromium-nickel steels 304 (1.4301) and 304L (1.4306 and 1.4307) have been used for many years to build technological devices in water and sewage treatment plants or pumping stations. These steels can be corrosive in aqueous environments with a high content of hydrogen sulphide and periodically increased chloride concentrations. The paper describes an example of fast-progressing corrosive damage of a screenings and grit separator, which after 2 years of operation perforations on the covers and in the part of wall above the sewage level. Microscopic observations confirmed the presence of living cells of bacteria and fungi on the walls of the screenings and grit separator. The fluorescent in situ hybridization (FISH) method showed the presence of sulfur bacteria (Acidithiobacillus thiooxidans) and bacteriafrom the γ- and δ-proteobacteria class. Studies have shown that the highest intensity of corrosion occurred in the parts of the screenings and grit separator exposed to humid air contaminated with hydrogen sulphide.
Keywords: stainless steel, pitting corrosion, sand remover, XRD, biological corrosion, fluorescence in situ hybridization (FISH)
2019, Vol. 62, nr 7, pp. 225-235, Ref. 27
CORROSION PROTECTION IN PRACTICE
Assessment of construction joints in the panel prefabricated buildings
Niezależny rzeczoznawca budowlany
This paper presents the characteristics of the large panel prefabricated buildings in Poland, prefabrication methods and the problem of the quality of realization of construction joints. The aggressiveness of the environment and their influence on individual elements of buildings were specified. The tests methods were described. The results of investigations, carried out in more than 300 open pits in buildings realized as technologies Szczecin, W70 / Wk70 and OWT. The results showed that the technical condition of the construction joints in examined buildings is satisfactory. There were no signs of degradation of concrete as well as corrosion of steel construction joints.
Keywords: large panel prefabricated buildings, examination of construction, construction joints
2019, Vol. 62, nr 7, pp. 236-239