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EN
Ni625/WC composite coatings added with different amounts of Y2O3 were prepared on the surface of 304 stainless steels by laser cladding. This study focused on the microstructure characteristics, microhardness, and corrosion performances of Ni625/WC composite coatings. The results showed that Y2O3 can effectively improve the corrosion resistance of the composite coatings. The microstructure from the bottom to the surface of composite coatings consists of plane crystal, cellular crystal, columnar crystal and equiaxed crystal. The Y2O3 content of optimum composite coating was 1.0%. Its microhardness was three times that of matrix material. In addition, the corrosion current density of the composite coating was only 2% of Ni625/WC coating, which was attributed to the good properties of Y2O3 and appropriate Y2O3 refined microstructure.
EN
This research examines the impact of different NaCl concentrations on the corrosion performance of AZ91D nanocomposites enhanced with nano metal oxides such as Zinc oxide (ZnO), Manganese oxide (MnO), and Titanium oxide (TiO2) through an electrochemical test method. The proposed materials were fabricated using a stir-squeeze casting process paired with an ultrasonication setup. In an argon gas-protected system, T6 heat treatment conditions were applied to these casted composites. The electrochemical corrosion results revealed that the ATO nanocomposite at 2.5% of NaCl concentration achieved lower corrosion current density (Icorr) (1.456 × 10–7 A/cm2) and higher corrosion potential (Ecorr) (− 1.08 V) owing to the formation of Mg2TiO3 precipitates, which act as a corrosion protective layer as well as reduce the corrosion rate. Based on the nyquist plot, the alloy and nanocomposites electron transfer rate were varied in the following sequence of AZD < AMO < AZO < ATO. The corroded samples Scanning Electron Microscope (SEM) and 3D profile image show ATO composites have minimum amount of crevice corrosion and peaks formation than other materials. Results from EDAX and elemental mapping confirm the presence of Mg2TiO3 precipitates on the ATO nanocomposite.
EN
In the field of surface engineering, thermal spraying is very wide adopted in many branches of the industry. The main reasons of such situation are its flexibility as well as cost effectiveness. Among others, High Velocity Oxy Fuel (HVOF) technique is dedicated for spraying hardmetal and cermet coatings, especially for wear- and corrosion resistance. Such type of coating could be a promising candidate as protective layer for magnesium alloys elements. These materials need a strong improvement in the corrosion protection as well as on the field of wear resistance in order to be widely used in the industry. In this work, different WC-based coatings, namely: (i) WC-Co, (ii) WC-Co-Cr and (iii) WC-Cr3C2-Ni manufactured by HVOF spraying, were investigated. The form of all feedstock materials was agglomerated and sintered powder. All coatings were sprayed with the same technological parameters, especially spray distance which was equal to 400 mm on the AZ91 magnesium alloy substrate. The main aim of the studies was to investigate the influence of the powder material on the corrosion resistance of obtained coatings. The manufactured coatings were examined in terms of its microstructure, using scanning electron microscope (SEM) and corrosion performance, which was assessed in the electrochemical corrosion investigations in 3.5% NaCl solution by Tafel method. The study showed that the corrosion resistance increasing in such order: AZ91 < WC-Cr3C2-Ni < WC-Co < WC-Co-Cr. It should be stressed that WC-Cr3C2-Ni coating exhibits very low corrosion performance, which could be effected by relatively high porosity (c.a. 3 vol.%) and because of that the more complex composition promotes creation of many corrosion cells.
EN
In this paper, a cold multi-pass extrusion process for a 15mm in diameter solid 2024-T3 aluminum alloy rod was carried out using three dies to obtain three different diameters of 14mm, 13mm, and 12mm. The microstructure, hardness, and corrosion behavior were investigated before and after the extrusion process. Load-Displacement data were recorded during each extrusion process. The electrochemical corrosion test was made in a 3.5 wt.% NaCl solution using potentiostat instrument under static potentials test. Corrosion current was recorded to determine the corrosion rate for specimens. The results showed that the extrusion load increased with the number of extrusion passes, which is also seen in hardness test results. In addition, the corrosion rate decreased with the increase in the number of extrusion passes. This is due to severe plastic deformation, which generates a fine grain structure of (AlCu) and (AlCuMg) components.
EN
The infuence of the zirconium diboride content and the method of initial material preparation on the corrosion properties of the composite on the 316L stainless steel matrix were determined. The powders were prepared in a Turbula mixer and a planetary mill. The corrosion properties were estimated on the basis of electrochemical tests, including open-circuit potential measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy. The presence of the ceramic phase changes the corrosion resistance of the tested materials due to porosity, which afects the corrosion mechanism. The standard potentiodynamic tests do not reveal poor corrosion resistance of porous materials, and only 24 h tests reveal accurate corrosion resistance of composite materials. Composites cannot go into a stable passive state because of the penetration of electrolytes into the pores and tend to oxidize systematically. 24-h corrosion tests indicate that samples prepared in a planetary mill show better corrosion resistance than those prepared in a Turbula mixer.
PL
W artykule opisano budowę zelektryfikowanego prądem stałym szlaku kolejowego. Zwrócono uwagę izolowanie elementów wiodących prąd trakcyjny w sieci zasilającej i powrotnej oraz na różnicę znaczenia tych izolacji. Podano przyczyny występowania prądów błądzących i ich charakter w dowolnym przekroju poprzecznym torowiska na szlaku. Wykazano warunki konieczne do ujawnianie się procesów elektrochemicznych na szynach torów szlakowych. Wykazano, że lokalnie na szlaku występują procesy galwanizacyjne – nakładania jonów elektrolitu glebowego na powierzchnię szyn i korozji elektrochemicznej – ubytku materiału szyn. Przy ruchu zelektryfikowanych pociągów na szlaku niezbędna jest wilgoć i styk szyn ze słabo odwodnionym podparciem stopki lub z tłuczniem – podsypką torowiska.
EN
The article describes the construction of a railway line electrified with direct current. Attention is paid to the isolation of the elements leading to the traction current in the supply and return network, and to the difference in significance of these insulations. The reasons for the occurrence of stray currents and their nature in any cross-section of the track on the trail are given. The necessary conditions for the disclosure of electrochemical processes on the rails of the track tracks were shown. It has been shown that the galvanization processes occur locally on the trail - the application of soil electrolyte ions on the surface of the rails and electrochemical corrosion - the loss of the rails material. During the movement of electrified trains on the route, moisture is necessary and the contact of the rails with the poorly drained support of the foot or with the ballast - track ballast.
PL
Na odporność korozyjną powłok zanurzeniowych wpływa wiele czynników takich jak temperatura, czas cynkowania, gatunek użytej stali, sposób chłodzenia, ale przede wszystkim skład chemiczny stopu cynkowniczego. Z historycznego punktu widzenia ołów używany był do ochrony wanny cynkowniczej oraz poprawienia właściwości lejnych stopu cynkowniczego. Uznanie ołowiu za toksyczny spowodowało użycie bizmutu jako jego zamiennika. Wpływ dodatków stopowych na odporność korozyjną powłok cynkowych na stalach o różnej reaktywności w kąpielach z dodatkiem ołowiu i bizmutu testowano w komorze solnej oraz technikami elektrochemicznymi. Za pomocą elektronowej mikroskopii skaningowej (SEM) analizowano grubości powłok oraz dystrybucję tych dodatków stopowych w powłokach, a także morfologię powłok. Zaobserwowano wpływ dodatków stopowych na przyspieszenie szybkości korozji powłok. Dodatki stopowe powodowały występowanie lokalnych procesów korozyjnych.
EN
The corrosion resistance of immersion coatings is the result of many factors such as temperature, time of galvanizing, the type of steel used, the cooling method, but above all the chemical composition of zinc melt. Historically, lead was used to protect the zinc bath and to improve the funnel properties of the zinc bath. The recognition of lead as toxic led to the use of bismuth as its substitute. The influence of alloy additives on the corrosion resistance of zinc coatings on steels with different lead and bismuth baths was tested in a salt chamber and by electrochemical techniques. The thickness of the coatings and the distribution of these alloy additives in the coatings as well as the phase distribution were analyzed using scanning electron microscopy (SEM). The influence of alloy additives on the acceleration of the corrosion rate of coatings was observed. Alloying additives induced the occurrence of localized corrosion processes.
8
Content available remote Głębokościowa charakterystyka odporności korozyjnej azotowanego stopu Ti6Al4V
PL
W pracy przedstawiono elektrochemiczną ocenę odporności korozyjnej azotowanego stopu tytanu Ti6Al4V. Badania korozyjne wykonano w 0,5M roztworze siarczanowym zakwaszonym do pH = 2 wykreślając krzywe potencjokinetyczne na różnych głębokościach warstwy wierzchniej. Grubość powstałej warstwy wierzchniej oceniono na podstawie badań strukturalnych oraz zmiany mikrotwardości na przekroju poprzecznym obrobionego powierzchniowo materiału. Stwierdzono, że przeprowadzona obróbka azotująca poprawia odporność korozyjną oraz znacznie utwardza powierzchnie badanego materiału. Uzyskana warstwa wierzchnia posiada budowę strefową przy czym najwyższą odporność korozyjną jak i najwyższą mikrotwardość wykazuje najbardziej zewnętrzna strefa azotków.
EN
The paper reports the electrochemical assessment of the corrosion resistance of the titanium alloy Ti6Al4V. Corrosion tests were carried out in a 0.5M sulphate solution acidified to pH = 2, while plotting potentiometric curves at varying depths of the top layer. The thickness of the produced top layer was assessed based on structural examination and change in microhardness over the cross-section of the surface treated material. It has been found that the nitriding treatment improves the corrosion resistance and considerably hardens the surface of the material under study. The obtained top layer exhibits a zonal structure, with the greatest corrosion resistance and the highest microhardness being shown by the outermost nitride zone.
PL
Artykuł ujmuje kompleksowo problemy korozyjne związane ze strukturą obwodów powrotnych wojskowych statków powietrznych o metalowej konstrukcji kadłuba. Autorzy opisują problemy związane z wykorzystaniem kadłuba jako obwodu powrotnego prądu elektrycznego, w szczególności z przewodami minusowymi łączącymi kadłub z zaciskami minusowymi odbiornika lub źródła, rzadko poruszane w literaturze naukowej z uwagi na "trywialność" zagadnienia. Aby zmniejszyć błąd pomiarowy, autorzy do pomiarów rezystancji poszycia kadłuba wykorzystują metodę techniczną o natężeniu prądu probierczego zwiększanego proporcjonalnie do pola powierzchni i stopnia sfałdowania powierzchni stykowej.
EN
The article comprehensively describes corrosion problems related to the structure of ground-return circuits of military aircraft with metal fuselage structure. The authors describe problems related to the usage of the fuselage as a ground-return circuit of electric current, especially with negative circuits connecting the fuselage with negative terminals of the receiver or the source, rarely discussed in the scientific literature due to the triviality of the problem. Given the necessity to reduce the measurement error, the authors use a technical method for measuring the resistance of the fuselage fabric covering with the intensity of test current increased in proportion to the surface area and the degree of folding the contact surface.
10
Content available remote Practical information on electrochemical corrosion of water pipelines
EN
Some aspects of drinking water ductile iron pipeline's electrochemical corrosion are discussed in this paper. We include: the impact of water parameters on its corrosivity, the relationships between the cement mortar lining and head loss to flow, pipeline diameter, and the total alkalinity of water, lifetime of the cement mortar lining. The discussion is lim ited strictly to some practical remarks with little theoretical background.
PL
Opisano wybrane aspekty elektrochemicznej korozji przewodów wodociągowych. Dyskusja ta dotyczyła: oceny korozyjności wody na podstawie jej parametrów fizyczno-chemicznych, wpływu wyprawy cementowej rurociągów na opory przepływu, związków pomiędzy jakością wody i oporami przepływu oraz trwałością wyprawy.
EN
Purpose: The presented research aims to determine the microstructural changes in weldments of commercially pure titanium Grade 1 after welding by hollow cathode arc discharge in vacuum and related changes in the corrosion behaviour of the weldments. Design/methodology/approach: Macro and microstructure of weldments were studied using optical microscopy. Corrosion behaviour of untreated Grade 1 and heat-affected zone of weldments of Grade 1 was investigated using electrochemical testing, including open circuit potential measurements and potentiodynamic polarisation. As an aggressive environment, 1 M KBr water solution was used. Findings: Welding by hollow cathode arc discharge in vacuum leads to the formation of a coarse Widmanstätten structure in the heat-affected zone. This imperfect structure results in a passive layer with worsened protective properties, thus increasing the corrosion rate of weldments by up to two orders of magnitude compared to Grade 1 in as-received condition. The passive layer on the welded surfaces did not allow Grade 1 to acquire a stable corrosion potential during potenitodynamic polarization. Research limitations/implications: Titanium and its alloys are passivating metallic materials, and their corrosion resistance depends on the properties of a thin protective surface layer. Changes in the underlying metal microstructure can affect the passivation behaviour of titanium and the properties of this layer. Welding by hollow cathode arc discharge in vacuum alters the microstructure of heat-affected zone, thereby causing Widmanstätten microstructure to form. As the passive layer over that microstructure has worsened protective properties, we suggest additional heat treatment after welding to be applied. Future experimental research on this topic is needed. Originality/value: Welding by hollow cathode arc discharge in vacuum is a welding method allowing weldments to be done in a clean environment and even in space. In the specialised literature, information on the structure and corrosion resistance of weldments of commercially pure titanium Grade 1 welded by hollow cathode arc discharge in vacuum is missing. The present research fills in a tiny part of this gap in our knowledge.
EN
In the present work, different Cu-alloyed model ductile irons with ferritic (0%Cu-0.09%Mn), mixed ferritic-pearlitic (0.38%Cu-0.40%Mn) and pearlitic (0.69%Cu-0.63%Mn) microstructure were produced and analyzed in terms of their electrochemical corrosion behavior in a 3.5wt.%NaCl aqueous solution containing naturally dissolved oxygen at room temperature (25°C). The remaining elements such as Si and Mg were kept at balanced levels in an attempt to minimize variations in graphite size and distribution among different samples. The corrosion resistance was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization. Microstructure analysis of the cast alloys confirmed similarity in the graphite morphology among the different cast samples and the expected variations in the metallic matrix. In the absence of passivation, it was found that the addition of copper led to an increase in corrosion resistance, which could be attested by higher values polarization resistance and corrosion potential.
EN
The Mg-Zn-Ca-(Cu,Au) alloys were considered as resorbable materials for orthopedic short- term implants. The aim of this paper was to determine the influence of Au and Cu addition on corrosion properties of Mg69Zn25Ca5Au1, Mg69Zn25Ca5Au0.5Cu0.5 and Mg69Zn25Ca5Cu1 metallic glasses. The analysis of corrosion results allowed to describe the influence of 0.5 and 1 at.% of Au and Cu on the corrosion resistance in artificial physiological fluid. The Mg69Zn25Ca5Au0.5Cu0.5 and Mg69Zn25Ca5Cu1 metallic glasses exhibit lower corrosion resis-tance in comparison with Mg69Zn25Ca5Au1 alloy. The increase of Cu content caused the increase of hydrogen evolution volume and the high cathodic activity. The Mg69Zn25Ca5Au1 metallic glass shows the decrease of hydrogen evolution volume and manifests the low corrosion current density and the high polarization resistance, indicating the high corrosion resistance.
PL
W artykule przedstawiono normalne i specjalne warunki pracy aparatury rozdzielczej. Podano przykłady narażeń środowiskowych. Omówiono zjawisko korozji elektrochemicznej. Przedstawiono próby urządzeń w oblodzeniu i wilgotne gorąco.
EN
The article presents normal and special service conditions switchgear and controlgear. Give for example environmental pollution. Characterization phenomenon electrochemical corrosion. Presents devices for low and high temperature and humidity test.
EN
The paper presents the results of the electrochemical corrosion tests of Inconel 600 and Inconel 625 laser-welded superalloys. The studies were conducted in order to assess the resistance to general and pitting corrosion in 3.5% NaCl solution. It was found that Inconel 600 possesses good corrosion resistance, however Inconel 625 is characterized by a greater resistance to general and also to pitting corrosion of the weld as well as the base metal.
EN
Cast stainless steel of the Cr-Ni duplex type is used, among others, for the cast parts of pumps and valves handling various chemically aggressive media. Therefore, the main problem discussed in this article is the problem of abrasion wear resistance in a mixture of SiC and water and resistance to electrochemical corrosion in a 3% NaCl- H2O solution of selected cast steel grades, i.e. typical duplex cast steel, high silicon and manganese duplex cast steel, and Cr-Ni austenitic cast steel (type AISI 316L). The study shows that the best abrasion wear resistance comparable to Ni-Hart cast iron was obtained in the cast duplex steel, where Ni was partially replaced with Mn and N. This cast steel was also characterized by the highest hardness and matrix microhardness among all the tested cast steel grades. The best resistance to electrochemical corrosion in 3% NaCl- H2O solution showed the cast duplex steel with high content of Cr, Mo and N. The addition of Ni plays rather insignificant role in the improvement of corrosion resistance of the materials tested.
EN
In the present study, the corrosion behaviour of A356 (Al-7Si-0.3Mg) alloy in 3.5% NaCl solution has been evaluated using cyclic/potentiodynamic polarization tests. The alloy was provided in the unmodified form and it was then modified with AlTi5B1 for grain refinement and with AlSr15 for Si modifications. These modifications yield to better mechanical properties. Tensile tests were performed. In addition, bifilm index and SDAS values were calculated and microstructure of the samples was investigated. As a result of the corrosion test, the Ecorr values for all conditions were determined approximately equal, and the samples were pitted rapidly. The degassing of the melt decreased the bifilm index (i.e. higher melt quality) and thereby the corrosion resistance was increased. The lowest corrosion rate was founded at degassing and as-received condition (3.9x10-3 mm/year). However, additive elements do not show the effect which degassing process shows.
18
Content available remote Fault diagnostics in a traction circuit by means of the stray current analysis
EN
This paper deals with the forming of stray currents in industrial spurs, stabling tracks and special purpose tracks near DC-electrified tracks. It describes methods which can be used to identify failures that lead to the occurrence of stray currents. Some innovative measuring methods are also introduced, all of them are based on results and knowledge obtained by practical experiments. The data and measurement results used in this paper come from measurements performed in the Bohumín railway station depot. It was found out that at this railway station, traction current leaked into the lightning control system. The method that was used in tracing these parasitic current paths, as well as the failures which led to the occurrence of these currents, are described in this paper.
PL
W artykule analizowano prądy rozproszone w bocznicach przemysłowych i torach w pobliżu trakcji DC. Pozwala to na wykrywanie uszkodzeń prowadzących do wzrostu tych prądów.
PL
Podjęto próbę eksperymentalnej oceny wpływu na wyniki badań impedancyjnych polaryzacji różnych fragmentów pobocznicy walcowego pręta zbrojeniowego. Pomiary metodą EIS przeprowadzono w układzie trójelektrodowym w roztworze wodnym modelującym ciecz porową betonu. Elektrodą badaną był gładki pręt zbrojeniowy ze stali RB500, przeciwelektrodą prostokątna blacha ze stali odpornej na korozję, a elektrodą referencyjną Cl–/AgCl,Ag. W badaniach zasięg polaryzacji różnicowano po obwodzie pręta, a jako drugą zmienną wprowadzono odległość przeciwelektrody od elektrody badanej. Analiza badań zasadniczo nie wykazała istotnego wpływu na wyniki opisanego sposobu polaryzacji.
EN
An attempt of experimental evaluation of the impact on the impedance test results on polarization of different parts of the circumferential cylindrical rebar was made. EIS measurements have been conducted using three-electrode system in an aqueous solution which models the concrete pore liquid. Working electrode was a smooth rebar made of steel RB 500 grade. The counter electrode was a rectangular sheet made of corrosion-resistant steel, and the reference electrode was Cl–/AgCl,Ag. In the test the polarisation range was differentiated along the circumference of the rod, and as a second variable was introduced the distance between the counter electrode and working electrode. The analysis of the tests generally showed no significant effect on the results of described polarization method.
20
Content available remote Monitoring the resistance of the military aircraft’s fuselage
EN
The article includes the description of the measurements of the military aircraft’s fuselage resistance, conducted for the purpose of identifying corroded spots in the fuselage’s mechanical connections’ structure. Considerations regarding the errors in measuring the single connections of the airframe’s mechanical element pairs and the entire structure of such connections in an actual aircraft are also presented. The paper includes the proposal of the superposition method for locating the mechanical connection pairs with improved electrical resistance. Simultaneously, for the purpose of forecasting the time of exploitation of the selected (most endangered) fuselage mechanical connections pairs, the article proposes conducting (in laboratory conditions) of the accelerated ageing process and converting the results to real-time using the Arrhenius method.
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