Sylvia Dundeková

Bio: Sylvia Dundeková is an academic researcher from University of Žilina. The author has contributed to research in topics: Corrosion & Surface finishing. The author has an hindex of 2, co-authored 10 publications receiving 12 citations.

Impact of Air Pollution and Climate Conditions on Carbon Steel in Slovak Republic

Abstract: The paper describes the impact of multi-pollution of atmosphere on carbon steel construction material in Slovak Republic. Corrosion like one of the most decisive factor determining the lifetime of material increases the risk of failure, which has considerable impact on maintenance costs. The objective of the article is to calculate potential material losses of carbon steel using the dose-response functions derived from the results of outdoor exposure program and by STN EN ISO 9223. The values were calculated and compared from 2003 to 2014. For comparison the impact of air pollution and climate condition maps of the mass loss and maps of the corrosion rate were created using 4-year averages - dates (2003-2006, 2007-2010 and 2011-2014). Actually, map of corrosion losses does not help to protect materials, but it can be useful for prediction of risks by design and analysis.

Corrosion Resistance of AISI 316Ti Stainless Steel Subjected to Shot Peening with and without Pickling in Various Chloride Environments

Abstract: Surface conditions of materials affect the chemical, physical and mechanical properties of stainless steels. The main interest of this paper is to focus on corrosion properties of the AISI 316Ti stainless steel treated by shot peening and shot peening and pickling. In the last years shot peening has been widely used as a method improving fatigue properties of components under cyclical load. Because surface finishing has strong effect on corrosion susceptibility of stainless steels, e. g. pitting and created pits can initialize cracks, it is important to analyse corrosion behaviour of the material in question. In this study, the tested surfaces were characterized by SEM, EDX analyses, measurement of surface free energy and roughness. Corrosion properties were investigated in various environments by exposure, potentiodynamic cyclic and EIS tests.

Electrochemical corrosion characteristics of phosphated S355J2 steel in sulfate environment

Abstract: Abstract Large number of mechanical and chemical surface pretreatment techniques is actually used on steels in industrial practice. Choosing the right combination of these technologies is one of the most important tasks for many applications. The purpose of this research was to evaluate the influence of selected mechanical surface preparation methods (grinding, sandblasting) on the quality and electrochemical corrosion characteristics of S355J2 steel before and after the final chemical surface treatment by the technology of manganese phosphating. The surface morphology of the formed phosphate layer was evaluated by a scanning electron microscopy (SEM) and the cross section analysis was performed by a light metallographic microscopy. 0.1M Na2SO4 solution simulating aggressive industrial pollution was selected for electrochemical corrosion tests. Impact evaluation of various mechanical and chemical surface treatments on the corrosion properties of the tested steel was realized by potentiodynamic polarization tests (PD) and electrochemical impedance spectroscopy (EIS) using the Tafel analysis and equivalent circuits method respectively. The obtained results proved that sandblasting negatively affected the corrosion resistance of S355J2 steel and subsequently created manganese phosphate layer.

Influence of the surface finishing on the corrosion behaviour of AISI 316L stainless steel

Abstract: The influence of the surface preparation of AISI 316L stainless steel by mechanical grinding, polishing and following passivation was examined by immersion corrosion tests in solution simulating body fluids. Decreasing of the surface roughness by finer preparation resulted in decrease of corrosion rates of AISI 316L stainless steel. Passivation of specimens resulted in decreasing of the corrosion rates and in decreasing of the corrosion process speed independently on the roughness of specimens before passivations. Lowest corrosion rates were observed in the case of polished and passivated specimens. However no significant difference in corrosion rates between polished and ground specimens with following passivation was observed.

Corrosion of steel by concrete

Abstract: The author details the reactions of various concretes on steel reinforcement. Although portland cements, slag cements and high alumina cements are all hydraulic binders, each possess special properties which are examined. The discussion of causes and methods of preventing the corrosion of steel reinforcement covers such aspects as galvanised steel reinforcement, effects of concrete composition, corrosion of steel reinforcments in concrete and prestressed reinforcement. It is concluded that the most significant influences on the corrosion of prestressing wire in concrete are: the presence of chloride; the presence of nitrates; the composition of the concrete; the degree of carbonation of the concrete; concrete compaction and, chlorides and sulphates should be used as far as possible when steel is embedded. (TRRL)

Electrochemical methods in tribocorrosion: a critical appraisal

Abstract: Tribocorrosion is an irreversible transformation of a material resulting from simultaneous physico-chemical and mechanical surface interactions in a tribological contact. Electrochemical methods are well suited for the study of tribocorrosion phenomena because they allow one to simulate the corrosive effect of the environment by imposing a fixed potential. Furthermore, the measurement of the anodic current permits one to determine the amount of material removed by oxidation as opposed to mechanical wear. In the present paper, experimental and theoretical aspects of applying electrochemical methods in tribology are discussed and recent results obtained with passivating metals in the authors' laboratory are presented. The importance of controlling the mechanical parameters and the contact geometry is stressed, and it is shown that these parameters can significantly affect the electrochemical response of a tribocorrosion system.

Complex corrosion properties of AISI 316L steel prepared by 3D printing technology for possible implant applications

Abstract: This paper deals with the investigation of complex corrosion properties of 3D printed AISI 316L steel and the influence of additional heat treatment on the resulting corrosion and mechanical parameters. There was an isotonic solution used for the simulation of the human body and a diluted sulfuric acid solution for the study of intergranular corrosion damage of the tested samples. There were significant microstructural changes found for each type of heat treatment at 650 and 1050 °C, which resulted in different corrosion properties of the tested samples. There were changes of corrosion potential, corrosion rate and polarization resistance found by the potentiodynamic polarization method. With regard to these results, the most appropriate heat treatment can be applied to applications with intended use in medicine.

Effect of phosphating time on protection properties of hurealite coating: Differences between ground and shot peened HSLA steel surface

Abstract: Shot peening is a standard surface treatment primarily used for enhancement of fatigue properties of metallic materials. However, its influence on surface properties is so radical, that subsequent techniques of surface treatment used on the shot peened surface need to be reconsidered in order to minimize the possible negative side effects of shot peening. In this case, the differences between hurealite formation on the ground and shot peened surfaces of modern high strength low alloy (HSLA) steel were evaluated by morphological and electrochemical corrosion observations and measurements. The surface morphologies of the formed coatings were observed by the scanning electron microscopy (SEM) and analysed by energy-dispersive X-ray analysis (EDX). The corrosion resistance of the HSLA steel with hurealite coating was evaluated using electrochemical impedance spectroscopy (EIS) by the analysis of Nyquist plots obtained in 0.1 M NaCl solution after various phosphating times on both types of pre-treated surfaces (ground and shot peened). The results showed that used technique of shot peening negatively influenced the phosphating process by prolonging the phosphating process in order to reach the coating with maximal protection properties in tested medium. Moreover, shot peened surface caused significantly enlarged size of the hurealite crystals and greater thickness of the coating compared to the surface pre-treated by grinding on the tested HSLA steel at the expense of a lower compactness and corrosion protection.

Effect of Surface Roughness on Oxidation Resistance of Stainless Steel AISI 316Ti During Exposure at High Temperature

Abstract: In the present work, the influence of surface roughness on oxidation kinetics of AISI 316Ti stainless steel and its consequences in term of oxidation resistance were investigated. Namely, the effect of surface roughness on oxidation resistance was evaluated during different types of cyclic oxidation tests at 900 and 1000 °C. The obtained results revealed that alloy possessing higher surface roughness showed longer lifetime compared to that with lower surface roughness. It was also found that more severe cyclic conditions suppressed the positive effect of surface roughness on sample’s lifetime. The better oxidation resistance of rougher alloy was correlated with suppressed formation of Fe-rich nodules on ground surfaces and explained by the combined effect of introduced defects in the near-surface region and possible increase in residual stresses caused by mechanical surface preparation.