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  • Author: J. Brezinová x
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Abstract

This paper presents the results of research aimed to measuring the corrosion properties of EDDQ steel sheet. The strain amount influence to the corrosion properties of the steel sheet for drawn parts has been proven by the modern methods of corrosion monitoring such as Electrochemical Impedance Spectroscopy. Corrosion rate was assessed using electrochemical methods in 0.1 M solution of NaCl. Experimental studies have pointed out if strain amount increases the corrosion rate of the steel sheet increases too.

Abstract

The paper presents results of research aimed at determining the corrosive properties of steel with cathode metal coating in selected corrosive environments. The corrosion properties of the tin coated steel were evaluated using electrochemical impedance spectroscopy and potentiodynamic tests. For realised measurements, distilled water, 0.5 mol dm−3 NaCl solution, 0.1 mol dm−3 NaCl solution and SARS, which simulates acid rain were used as corrosive solutions. Both corrosion methods are suitable for diagnosing corrosion properties of steel with metal coatings.

Abstract

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.

Abstract

The surface treatment by a powder coating is one of the progressive technologies. Such coatings are resistant to corrosion and mechanical wearing. The quality of surface protection is affected primarily by a layer pre-treatment, the type of surface tretment, the system selection and the method and quality of application. Taking into account all the surface pre-tretment methods, the chemical pre-modification is a leading method. One of the methods is pre-treatment using a conversion coating which was developed on the nanotechnology basis - BONDRITE NT. That non-phosphate chemical pre-treatment is utilized at a surrounding temperature. It creates nano-ceramic protective layer on steel, zinc and aluminium surfaces, and as the result the coating has a significant adhesion. In the paper, the possibilities for the improvement of corrosion resistance of powder coatings using the subject conversion coating are presented at the current pasivation of respective surface.

Abstract

The article is aimed at evaluation of chosen properties of thermally sprayed coatings based on tungsten carbide. It was evaluated two types of coatings – WC-FeCrAl and WC-WB-Co. The coatings were deposited on basic material steel AISI 316L. The aim of experimental works was to determine the quality and resistance of coatings in corrosion environment depending on number of thermal cycles. The quality of coatings was evaluated by determination of their adhesion depending on thermal cycles, determination of microhardness and indentation fracture toughness. Coatings were exposed in tribo-corrosion conditions with the presence of 1% NaCl. The results of experimental showed a higher quality of coating WC-WB-Co.

Abstract

Phenolics are the most widely distributed class of plant secondary metabolites and higher plants are able to produce several thousand different phenolic compounds. It has been reported that phenolics are more resistant to decomposition due to the negative impact on the microorganisms involved. Therefore, it may be hypothesized that the higher content of phenolics in plant tissue may cause slower decomposition rates and potentially higher carbon sequestration in the soil. The primary goal of this study was to evaluate and compare the content of phenolics in seven common macrophytes in the Czech Republic. Aboveground biomass was sampled in June 2016 at seven different localities and phenolics concentrations determined by spectrophotometric methods according to the Folin-Cioacalteau method ranged from 9.02 to 28.39 g kg−1 dry biomass weight (DW). Several plants were also harvested in August, October and December in order to follow a seasonal pattern. According to the results it seems that surveyed macrophytes vary widely in phenolics concentrations in relation to sampled site, harvesting time, plant species, and plant parts as well.

Abstract

The paper deals with evaluation the corrosion characteristics of welded joints in two corrosion environments – SARS and 0.1 M NaCl solution. Welds were made by MAG technology using three protective gas mixtures - Ferroline He20C8, Ferroline C18 and Ferroline C6X1. There were realised chemical analysis of the base material and weld metal of all welded joints, Vickers hardness test of the base material, heat affected zones and weld metals, metallographic analysis of all areas of welds and measurement of base and weld metal corrosion rate in two corrosion environments. Hardness increases from the base material through the HAZ to the weld metal. The maximum difference between the hardness of the weld metal and the base material is 36 HV 0.1 - realised welds do not show a notch effect. The corrosion rate of the materials in SARS solution was higher than in the NaCl solution. The corrosion rate in weld metals of all welded joints was lower than the corrosion rate of the base material. The lowest corrosion rate in both corrosive environments showed a weld metal made using shielding gas Ferroline C18.

Abstract

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).