Search

Corrosion is a spontaneous process that can be slowed down, though not entirely prevented, through various methods. The most common method for protecting metals against corrosion involves the application of coatings, with nearly three-quarters of metal structures currently benefiting from organic coatings. In addition to providing effective corrosion protection, modern coatings are expected to be environmentally friendly. Presently, there is growing interest in researching coatings based on water-soluble natural polymers containing active chemical compounds, such as corrosion inhibitors. One such polymer is chitosan, which exhibits excellent film-forming ability in acidic aqueous solutions, making it well suited for diverse protective coating applications. This study explores the possibility of applying a chitosan-based coating with the addition of TiO2 and eucalyptol for the protection of steel against acid corrosion. The results confirmed that the tested chitosan-based coatings must incorporate an inhibitor to have a protective effect on the steel surface, since these coatings show a corrosive effect without an inhibitor. Although coatings based on chitosan and titanium dioxide with the addition of eucalyptol demonstrate protective effects, the duration of these effects is limited. Consequently, this method of protection could be suitable only for temporary protection of steel against acid corrosion. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

U ovom pregledu prikazan je dio znanstvenih istraživanja pri razvoju legura s prisjetljivošću oblika (engl. Shape Memory Alloy, SMA) na bazi bakra na Metalurškom fakultetu Sveučilišta u Zagrebu u razdoblju od 2006. do 2022. godine u suradnji s brojnim visokoškolskim i znanstvenim institucijama u regiji. Istraživane su sljedeće legure SMA: CuAlNi, CuAlMn, itd. Provedeno je fizikalno modeliranje uključujući numeričku simulaciju razvoja mikrostrukture i toplinsku analizu tih legura. Legure SMA rađene su u lučnoj, visokofrekventnoj i indukcijskim pećima pomoću tri različite tehnologije lijevanja: brzo skrućivanje, lijevanje u metalne i/ili grafitne kokile te kontinuirano lijevanje u šipke. Nakon toga odabrane legure su toplo i hladno valjane. Provedena je toplinska obrada (austenitizacija uz naknadno gašenje u vodi i žarenje) i karakterizacija funkcionalnih svojstava legura SMA u različitim stanjima. Za karakterizaciju, osim ispitivanja mehaničkih svojstava, primijenjene su brojne visokosofisticirane metode: optička mikroskopija (OM), pretražna (SEM) i transmisijska elektronska mikroskopija (TEM), energetsko disperzijska-spektroskopija (EDS), pretražna diferencijalna kalorimetrija (DSC), dinamičko-mehanička analiza (DMA), rendgenska difrakcija (XRD), elektrokemijska impedancijska spektroskopija (EIS) itd. Već pri lijevanju kod pojedinih legura SMA, a posebice nakon toplinske obrade austenitizacijom uz naknadno gašenje u vodi, utvrđena je martenzitna mikrostruktura koja je osnovni preduvjet za svojstvo prisjetljivosti oblika. Na temelju provedenih istraživanja po većini parametara (plastičnost, korozijska otpornost itd.) može se zaključiti da su se najbolje pokazale legure CuAlMn. Kao rezultat provedenih istraživanja na legurama SMA, prema podatcima iz baze CROSBI (na dan 23. prosinca 2022.), istraživački tim objavio je 33 rada u časopisima (od kojih su 23 rada u časopisima indeksiranim u bazi podataka Web of Science), 74 rada u zbornicima međunarodnih konferencija, 18 sažetaka u zbornicima konferencija te pet ostalih radova. Također, obranjena je jedna doktorska disertacija te je izrađeno i obranjeno 12 završnih i 25 diplomskih radova u području tehničkih znanosti iz znanstvenih polja metalurgije i kemijskog inženjerstva.

U ovom radu prikazano je istraživanje korozije 15Mo3 cijevi u sustavu grijača vodene pare termoelektrane Plomin. Korozijsko oštećenje dovelo je do puknuća cijevi u sustavu te zastoja u radu. U radu je analiziran uzorak puknute cijevi, a potrebno je bilo odrediti vrstu korozije i uzrok korozije. Korozija se dijeli prema tri faktora: mehanizmu djelovanja, specifičnosti nastanka i obliku korozijskog napada. Opisana su elektroenergetska postrojenja s naglaskom na termoelektrane uz analizu sustava u kojem je došlo do korozijskog oštećenja cijevi parnog kotla termoelektrane. Prikazani su rezultati istraživanja korozijskih produkata na cijevi te izgled same pukotine. Provedena su istraživanja kemijskog sastava, ispitivanja tvrdoće prema Vickersu i analiza FT-IR spektroskopijom te mikroskopska istraživanja svjetlosnom i elektronskom mikroskopijom. Na ispitanom uzorku oštećene cijevi parnog kotla dokazano je da je uzrok nastalog oštećenja erozijska korozija.

Copyright of Materials Protection (0351-9465) is the property of Engineers Society for Corrosion Republic of Serbia, Belgrade and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials Protection (0351-9465) is the property of Engineers Society for Corrosion Republic of Serbia, Belgrade and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this research, the effect of accumulative extrusion bonding (AEB) on the microstructure and mechanical properties of Mg-0.8Mn-0.5Ca biocompatible alloy was investigated. The goal of this research was to develop the mechanical and corrosion properties of Mg-0.8Mn-0.5Ca alloy after ABE process as a novel severe plastic deformation process. The simulation of AEB process showed that the average effective strain per pass for channels with the internal angle of 120° was about 1.93. The average grain size was dramatically decreased from about 448.3 µm for the homogenized alloy to 1.55 µm for the 3-pass processed sample. Microstructural observations suggested a combination of continuous, discontinuous, and twinning-induced dynamic recrystallization as the major mechanisms of grain refinement. Tensile and compressive strengths were improved from 150 and 205 MPa to 330 and 301 MPa after three passes of AEB, indicating 2 and 1.5 times improvements, respectively. Tensile elongation decreased from 26% for the homogenized sample to 7.5% for the 3-pass processed sample due to the severe work-hardening, non-uniform strains, and inhomogeneous microstructure produced by the ABE process. Corrosion resistance in SBF solution was improved from 1.1 to 14.159 after three passes of ABE due to the presence of hydroxyapatite formed on the surface of the AEBed samples. [ABSTRACT FROM AUTHOR]

This paper presents the investigation of corrosion of 15Mo3 pipe in the steam heater system of the Plomin thermal power plant. Corrosion damage led to a rupture in the system as well as delays. Therefore it was necessary to determine the type and the cause of the corrosion. Corrosion is classified according to three factors: the mechanism, the specificity of its occurrence, and the form of the corrosion attack. Power plants are explained with an emphasis on thermal power plants, along with an analysis of the sample and system in which the damage occurred. The results of the investigation of corrosion products on the pipe and the rupture itself are presented. Chemical analysis, microscopic research with light and electron microscopy, hardness tests according to Vickers, and analysis with FT-IR spectroscopy were carried out. Erosion corrosion was proven to be the cause of the failure in a specific example. [ABSTRACT FROM AUTHOR]

This review presents part of scientific research in the development of shape memory alloys (SMA) based on copper at the Faculty of Metallurgy of the University of Zagreb in the period from 2006 to 2022, in cooperation with a number of universities and scientific institutions in the region. The following SMA alloys were studied: CuAlNi, CuAlMn, etc. Physical modelling, including numerical simulation of microstructure evolution and thermal analysis were performed. The SMA alloys were produced in arc, high-frequency, and induction furnaces by means of three different technologies: melt spinning, casting in metallic and/or graphite moulds, and continuous casting in bars. The selected SMA alloys were then hot and cold rolled. The heat treatment (quenching and tempering) and the characterisation of the functional properties of the SMA alloys under the different conditions were carried out. Numerous sophisticated methods were used to characterise the functional properties, in addition to testing the mechanical properties: optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), etc. According to several parameters (ductility, corrosion resistance, etc.), it could be concluded that CuAlMn was the best alloy. As results of this investigation on SMA alloys, according to the CROSBI database (by December 23, 2022), the research team has published 33 articles in journals (including 23 articles in journals indexed in the Web of Science database), 74 papers in proceedings of international conferences, 18 abstracts in proceedings of conferences, and 5 other papers. In addition, 1 doctoral thesis, 12 bachelor theses, and 25 master theses were prepared and defended in the field of technical sciences in the areas of metallurgy and chemical engineering. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Brojna su propitivanja potrebe rutinskog odstranjenja metalnog implantata nakon saniranja prijeloma kosti. Pretežita indikacija za odstranjenje jest slabljenje mehaničkih svojstava i pucanje implantata prije cijeljenja kosti. Cilj ovog istraživanja bio je ispitati mehanička svojstva osteosintetske pločice izrađene od standardnoga kirurškog čelika u simuliranim biološkim uvjetima. U istraživanju smo koristili implantate nehrđajućeg čelika 316L i pohranili ih kroz godinu dana u simuliranome biološkom mediju (engl. SBF – simulated body fluid). Analizirano je 48 pločica standardnoga kirurškog čelika podijeljeno u četiri skupine. Jedna je kontrolna. Ostale su bile uronjene u otopine različitih pH vrijednosti. Uronjene pločice testirane su nakon godinu dana, a kontrolna odmah na početku istraživanja. Tijekom godinu dana analizirala se promjena mikrostrukture uronjenih pločica skenirajući elektronskim mikroskopom (SEM) u pet navrata, a kontrolna grupa samo jednom. Na pločicama koje su bile u biološkim simuliranim uvjetima, bez obzira na pH medija, značajno je veći broj jamičastih korozija kod mjerenja nakon šest mjeseci i godinu dana. Nakon godinu dana pohrane u medijima različite pH mjerene su vrijednosti mehaničkog, statičkog i dinamičkog opterećenja pločica. Niti jedno načinjeno mehaničko testiranje nije pokazalo statistički značajnu razliku između kontrolne skupine pločica i onih koje su bile u biološki simuliranim uvjetima kroz godinu dana. Nepromijenjena mehanička svojstava istraživanih implantata, unatoč značajnim promjenama mikrostrukture nastale kao posljedica jamičaste korozije u biološki simuliranim uvjetima, otklanjaju vjerojatnost slabljenja pločice kao i indikaciju za njezino odstranjenje u tom vremenskom razdoblju.

This research focuses on studying the mechanical, tribological, and corrosion behaviors of alloy steels: AISI 4340, AISI 5140, and AISI 8620 by laser hardening, respectively. In light of the tests which have been carried out meticulously, it is concluded that the optimum laser hardening parameter for all steel grades is 4 mm/s scanning speed and 1300 °C surface temperature. Micro-structural changes, Vickers hardness as mechanical properties, and tribological properties with reciprocating wear tests were carried out. Furthermore, corrosion tests were conducted. The test results reveal that the maximum hardness is achieved 50-300 µm below the surface for all laser-hardened steels. Additionally, this study demonstrates that the wear resistance of steel is enhanced by the implementation of laser hardening. This study also determines that laser hardening has a positive impact on lifting the corrosion resistance behavior of AISI 4340 steel. In contrast, the corrosion resistance properties of AISI 8620 steel were reduced nearly by 54.17%. [ABSTRACT FROM AUTHOR]

Copyright of Lijecnicki Vjesnik is the property of Croatian Medical Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arheološki Vestnik is the property of Scientific Research Centre of Slovenian Academy of Sciences & Arts and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metalų korozija viena iš problemų eksploatuojant įrengimus, mechanizmus, kurie yra sudaryti ar pagaminti iš metalinių konstrukcijų, kurios koroduoja dėl fizikinės ir cheminės sąveikos su aplinka. Siekiant sustabdyti korozijos procesą, būtina identifikuoti faktorius, kurie lemia korozijos procesą eksploatuojamos konstrukcijos ar mechanizmo. Straipsnyje analizuojami faktoriai lemiantys korozijos procesą. Siekiant įvertinti koroziją lemiančius faktorius ir imtis prevencijos priemonių korozijos procesui valdyti, atliktas analitinis tyrimas, kurio metu nustatyti faktoriai lemiantys korozijos dydį: vandens temperatūra, jūros druskos kiekis vandenyje, pH, laivo balastinio valymo procesui naudojama Cl koncentracija bei laivo eksploatacijos laikas.

Copyright of Rudarsko-Geolosko-Naftni Zbornik is the property of Faculty of Mining, Geology & Petroleum Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Archaeology & Science / Arheologija i Prirodne Nauke is the property of Institute of Archaeology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Od utemeljenja Zavoda, akademske godine 1961./62., njegova znanstveno-istraživačka djelatnost bila je usmjerena na elektrokemijska istraživanja metala, pojavu pasiviteta i inhibiciju korozije. Kasnije, ponajprije primjenom elektrokemijskih metoda, proučavaju se fenomeni na granici faza metal│anodni sloj│elektrolitna otopina koji su od značaja za kemijske izvore struje i poluvodičke sustave. Tijekom posljednjih deset godina istraživanja se usmjeravaju u dva smjera: i) ispitivanje utjecaja legirajućih elemenata na dizajn otpornih materijala i biofunkcionalizacija površine biorazgradljivih i biokompatibilnih metalnih implantata; ii) modifikaciju elektroda i njihovih površina u svrhu razvoja novih elektroanalitičkih metoda za određivanje teških metala i biomolekula.

U ovom radu istražen je utjecaj komercijalnog inhibitora (Chemtec FI30) na proces korozije ugljičnog čelika P235 u različitim vodenim otopinama; demineraliziranoj i/ili vodovodnoj vodi uz dodatak komercijalnog biocida (Chemtec BI01). Istraživanja su provedena gravimetrijskom metodom i elektrokemijskim metodama, dok je površina ispitivanog materijala analizirana pomoću optičkog mikroskopa. Analize pokazuju da inhibitor smanjuje brzinu korozije ugljičnog čelika u ispitivanim otopinama, ima visoku djelotvornost te da se može svrstati u anodne inhibitore. Također, uočeno je da inhibitor smanjuje opću i jamičastu koroziju ugljičnog čelika u korozivnim vodenim otopinama.

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A comparative corrosion study of Cu and Cu-Ai, Cu-Ai-Ni, Cu-Ai-Mn and Cu-Ai-Mn-Ni in 0.5 moi dm3 NaCl solution was performed using an open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy measurements (EiS). Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) analysis was used to evaluate corrosive damage on the sample surface after polarization measurements. The reported results suggest that the alloying elements have reduced cathodic and anodic current densities in the Tafei region, increased anodic currents at higher anodic potentials, and slightly displaced corrosion potential towards more positive values. Overall, impedance increased in the following order: Cu < Cu-Ai < Cu-Ai-Ni < Cu-Al-Mn < Cu-Al-Mn-Ni. This indicates that Cu alloys possess better corrosion resistance. SEM and EDS analysis after polarization measurements showed uniform dissolution of pure Cu, as well as the presence of a surface oxide layer, consisting of a mixture of the corresponding alloying elements, on all investigated alloys. Aggressive anodic polarization severely damaged the barrier layers on the Cu alloy specimens. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plasma spray Cr2O3 ceramic layers are used as a separate coating or as a supplement to bio-reactive organic composite ceramics Ca10(PO4)6(OH)2-Al2O3-ZrO2-Cr2O3 and other bio-inert ceramics in composites of the types Al2O3–ZrO2–SrO–Cr2O3–Y2O3, ZrO2-TiO2-Cr2O3 and TiO2-Cr2O3 to increase the mechanical properties and resistance components of artificial joints on sliding abrasion and corrosion. This paper analyzes the influence of the plasma gun distance from the substrate on the mechanical properties and the microstructure of Cr2O3 layers deposited with the current of 40kW. The aim was to deposit layers with optimal characteristics that will enable the effective implementation of Cr2O3 layers on substrates of steel implants exposed to dry friction without lubrication and to corrosion of living tissues. The mechanical properties were tested by examining microhardness layers using the HV0.3 method and the strength was tested by tensile testing. The surface of powder particles was examined by SEM. The microstructures of layers were analyzed with the use of an optical microscope (OM) and a scanning electron microscope (SEM). The test results confirmed a possibility of effective application of bio-inert layers of Cr2O3 with other ceramics intended for the production of functional implants. / Метод плазменного напыления керамических Cr2O3 покрытий применяется как самостоятельное покрытие, так и в качестве дополнения к биоактивной органической композиционной керамике Ca10(PO4)6(OH)2-Al2O3-ZrO2-Cr2O3 и к иным биоинертным керамикам, создавая композиты типа Al2O3–ZrO2–SrO–Cr2O3– Y2O3, ZrO2-TiO2-Cr2O3 и TiO2-Cr2O3 с целью улучшения механических характеристик и повышения стойкости к износу и коррозии компонентов протеза сустава. В данной статье представлено каким образом расстояние между пистолетом для плазменного напыления и обрабатываемой поверхностью влияет на механические характеристики и микроструктуру Cr2O3 слоев покрытия, нанесенных при электоромощности 40 кВт. Цель нанесения различных слоев заключалась в определении лучших характеристик, которые обеспечат эффективное применение покрытия Cr2O3 для подложек металлических имплантатов, подверженных сухому трению без смазки, а также коррозии живых тканей. Анализ механических характеристик покрытия проведен на основании испытаний микротвердости методом HV0.3 и прочности соединений методом растяжения. Структура слоев испытана методом оптической микроскопии (ОМ), а поверхность испытана методом электронной микрографии (SEM). На основании полученных характеристик установлено, что эффективное применение биоинертных слоев Cr2O3 возможно и в сочетании с другими керамическими покрытиями, предназначенными для изготовления функциональных имплантатов. / Plazma sprej keramički slojevi Cr2O3 koriste se kao zasebna prevlaka ili kao dodatak bioreaktivnoj organskoj kompozitnoj keramici Ca10(PO4)6(OH)2-Al2O3-ZrO2-Cr2O3 i drugim bioinertnim keramikama, praveći kompozi tipa Al2O3-ZrO2-SrO-Cr2O3-Y2O3, ZrO2-TiO2-Cr2O3 i TiO2-Cr2O3 za povećanje mehaničkih karakteristika i otpornosti komponenti veštačkog zgloba na habanje klizanjem i koroziju. U radu je analiziran uticaj odstojanja plazma pištolja od podloge na mehaničke karakteristike i mikrostrukturu Cr2O3 slojeva deponovanih sa snagom napajanja od 40 kW. Cilj rada bio je da se deponuju slojevi optimalnih karakteristika koji će omogućiti efikasnu primenu Cr2O3 slojeva na podlogama čeličnih implantata izloženih suvom trenju bez podmazivanja i koroziji živih tkiva. Ispitivanje mehaničkih karakteristika realizovano je ispitivanjem mikrotvrdoće slojeva metodom HV0.3 i čvrstoće spoja metodom na zatezanje. Izgled površine čestica praha ispitan je metodom SEM. Mikrostrukture slojeva analizirane su uz primenu optičkog mikroskopa (OM) i skening elektronskog mikroskopa (SEM). Rezultati ispitivanja potvrdili su mogućnost efikasne primene bioinertnih slojeva Cr2O3 sa drugim keramikama namenjenim za izradu funkcionalnih implantata.

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the establishment of the Department of General and Inorganic Chemistry in 1961, at the Faculty of Chemistry and Technology, University of Split, its scientific interest and investigations were focused toward electrochemical research. Consequently, electrochemistry became the backbone of the scientific research and development of the Department. In the last 10 years, scientific interest has been focused on the influence of alloying elements on design of corrosion resistance materials, as well as biofunctionalisation of biodegradable and biocompatible metal-based implants. In addition, development of various electroanalytical methods based on modified electrodes as sensing part of sensors, have been in focus in the recent period. The developed sensors were used for determination of heavy metals or biomolecules. [ABSTRACT FROM AUTHOR]

The effect of a commercial inhibitor (Chemtec FI30) on the corrosion of P235 carbon steel in water (demineralised and/or tap water) with the addition of a commercial biocide (Chemtec BI01) was studied in the present work. This study was carried out by weight loss and electrochemical methods, while specimen’s surface was examined using optical microscope. Results obtained from gravimetric measurement revealed that P235 carbon steel corroded in aqueous solution, i.e., in a solution of demineralised and tap water (50 : 50) and a biocide (Fig. 1), and in tap water with a biocide (Fig. 5). By analysing the surface of carbon steel with an optical microscope, general and pitting corrosion was observed, which was more pronounced in tap water with biocide (Figs. 2 and 6). The addition of a commercial inhibitor significantly reduced the occurrence of corrosion damage on the surface of carbon steel (Figs. 3, 4, 7, and 8) and decreased the rate of carbon steel corrosion in all aqueous solutions (Table 1). Electrochemical investigations performed by open circuit potential measurement, linear polarisation and potentiodynamic polarisation measurement showed that the inhibitor Chemtec FI03 shifted the potential to more positive values (Figs. 9 and 10), increased polarisation resistance (Table 3), decreased the rate of carbon steel corrosion, and had high efficiency in all tested solutions (Table 4). The results obtained showed that this commercial inhibitor could be used as an effective inhibitor for the corrosion of carbon steel in aqueous media. [ABSTRACT FROM AUTHOR]

In this paper, an attempt was made to improve the corrosion resistance of activated tungsten inert gas welded super duplex stainless steel such as UNS S 32750. Joints were fabricated by fluctuating the important process parameters such as welding speed, shielding gas flow rate and welding current, using NiO as activation flux. A central composited design model was developed for identification of the Activated Tungsten Inert Gas welding process parameter values for fabricating twenty joints. The welded joints were subjected to pitting corrosion test using an electrochemical corrosion testing system and salt spray testing was done for 48 h. Empirical relationships were developed for the process parameters with variations in the pitting potential and the rate of mass loss. The significance of the developed model was ascertained using analysis of variance method and optimization was done using response surface methodology. The joints fabricated at welding speed of 54.26 mm/min, welding current of 157 A and gas flow rate of 14.8 L/min, were found to have maximum pitting potential of -252.36 eV and minimum mass loss of 0.0108 g. Using validation experiments, the error was identified within three percentage which indicated that the optimization model was developed with very high predictability. [ABSTRACT FROM AUTHOR]

Na armiranobetonskim konstrukcijama izloženim agresivnom okolišu često nastaju oštećenja uslijed korozije armature izazvane kloridnim ionima. Oštećenja nastaju u obliku pukotina i odlamanja zaštitnog sloja betona uslijed bubrenja produkata korozije, što nepovoljno utječe na nosivost i trajnost konstrukcije. Povrh toga, površina poprečnog presjeka armature smanjuje se istovremeno s procesom degradacije betona. No, oštećenja se javljaju neposredno nakon depasivacije čelika uslijed kritične koncentracije kloridnih iona u blizini armature. Vrijeme koje je potrebno da kritična koncentracija kloridnih iona prodre do armature naziva se faza inicijacije, a osnovni cilj ovog rada je procjena njezinog trajanja. Trajanje faze inicijacije moguće je predvidjeti ukoliko se u obzir uzmu transportni procesi koji se odvijaju kroz zaštitni sloj betona. Najvažniji fizikalni procesi vezani uz fazu inicijacije su transport kapilarne vode, kloridnih iona te topline. Stoga je u okviru ovog rada razvijen 2D numerički model pomoću metode konačnih razlika, koji simulira navedene transportne procese. Primjena modela pokazana je na numeričkom primjeru u kojem je kvadratni poprečni presjek armiranobetonskog stupa izložen agresivnim morskim uvjetima. Proračun je proveden kako bi se istražio utjecaj širine pukotina na trajanje faze inicijacije. Numerički rezultati pokazuju da raspucalost zaštitnog sloja betona značajno smanjuje trajanje faze inicijacije, a samim time i uporabni vijek konstrukcija.

Zaštita čeličnih elemenata bitan je proces u proizvodnji čeličnih konstrukcija. U svrhu zaštite od pojave korozije i vanjskog utjecaja okoline, sve čelične konstrukcije potrebno je zaštititi na adekvatan način. Kvaliteta antikorozivne zaštite jedan je od osnovnih uvjeta za osiguranje dugotrajnosti konstrukcije te se dobro izvedenom zaštitom produljuje njezin uporabni vijek. Tehnologija nanošenja zaštite primjenom premaza zahtjevan je proces koji traži dobro poznavanje svih koraka u zaštiti konstrukcije, od odabira sustava premaza, pripreme površine do sušenja. U radu je opisana antikorozivna zaštita čeličnih konstrukcija primjenom zaštitnih premaza, kako odabrati odgovarajući sustav premaza, šta utječe na njegov odabir, kako pripremiti površinu koja se zaštićuje te koji sustavi premaza se koriste ovisno o kategoriji atmosferske korozivnosti.

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present study, the corrosion mechanism of commercial FeCrAl alloy (Kanthal AF) during annealing in nitrogen gas (4.6) at 900 °C and 1200 °C is outlined. Isothermal and thermo-cyclic tests with varying total exposure times, heating rates, and annealing temperatures were performed. Oxidation test in air and nitrogen gas were carried out by thermogravimetric analysis. The microstructure is characterized by scanning electron microscopy (SEM-EDX), Auger electron spectroscopy (AES), and focused ion beam (FIB-EDX) analysis. The results show that the progression of corrosion takes place through the formation of localized subsurface nitridation regions, composed of AlNphase particles, which reduces the aluminum activity and causes embrittlement and spallation. The processes of Al-nitride formation and Al-oxide scale growth depend on annealing temperature and heating rate. It was found that nitridation of the FeCrAl alloy is a faster process than oxidation during annealing in a nitrogen gas with low oxygen partial pressure and represents the main cause of alloy degradation. [ABSTRACT FROM AUTHOR]

The atmospheric plasma spray process is one of the procedures used for the deposition of coatings resistant to wear due to friction, erosion, cavitation and corrosion. In this paper, the APS process produced a Cu10wt.%Al intermetallic coating which is a reliable candidate for use in tribological environments because of a combination of low price and exceptional resistance to abrasion under different work conditions. The aim of this study was to investigate the mechanical properties and the structure of the Cu10wt.%Al intermetallic coating and develop an efficient method for repairing and improving light alloy resistance to wear. Many components of copper alloys tend to be degraded due to corrosive environment, friction, erosion and cavitation. Such components can be saved by surface engineering with the use of appropriate coatings on surface areas exposed to degradation. A typical microstructure of a coating for the APS process is lamellar, with micro pores, unmelted particles, inter- lamellar oxides and precipitates present in it. The mechanical properties of Cu10wt.% Al coatings were investigated by measuring the microhardness of coating layers using the HV0.3 method while the bond strength was tested on a tensile machine. The morphologies of powder particles and the coating surfaces were analyzed on a scanning electron microscope (SEM). The analysis of the coating microstructure was carried out with the use of an optical microscope, and a share of micro pores was determined by analyzing the micrographs through an optical microscope (OM). / Плазменное напыление является одним из методов нанесения износостойких покрытий, устойчивых в т.ч. к истеранию, эрозии, кавитации и коррозии. В данной работе описан процесс создания интерметаллического покрытия Cu10вес.%Al, являющегося надежным кандидатом для применения в трибологических условиях эксплуатации. Преимуществом покрытия данного вида является сочетание низкой стоимости и повышенной стойкости к абразии в различных режимах эксплуатации. Цель данного исследования заключается в изучении механических свойств и структур интерметаллических покрытий Cu10вес.%Al и развитии эффективной методологии нанесения покрытия, а также в повышении износостойкости легких сплавов. Многие компоненты сплава меди в коррозийных условиях подвергаются кавитационному и эрозийному разрушению, но своевременная инженерия поверхности соответсвующим покрытием деградирующих слоев, поможет сохранить их. Типичная микроструктура покрытия напылением – ламеллярная, с микропорами, несплавленными частицами, межламеллярными оксидами и преципитатами. Испытания механических характеристик покрытия Cu10вес.%Al проводились методом HV0.3 а испытания прочности соединений − методом растяжения. Морфология частиц порошка и поверхности покрытия испытаны методом электронной микрографии (SEM) . Испытания микроструктуры покрытия проведены методом оптической микроскопии, а микропоры исследованы методом оптической микрографии ( ОМ). / Atmosferski plazma sprej je jedan od postupaka koji se koristi za depoziciju prevlaka otpornih na habanje usled trenja, erozije, kavitacije i korozije. U ovom radu, APS postupkom proizvedena je intermetalna prevlaka Cu10tež.%Al, koja je pouzdana za primenu u tribološkim okruženjima zbog kombinacije niske cene i izuzetne otpornosti na abraziju pri različitim uslovima rada. Cilj ovoga rada bio je da se izuče mehanička svojstva i struktura intermetalne prevlake Cu10tež.%Al i razvije efikasan metod za reparaciju i poboljšanje otpornosti lakih legura na habanje. Mnoge komponente od legure bakra imaju tendenciju da se degradiraju zbog korozivne sredine, trenja, erozije i kavitacije. Takve komponente mogu se spasti inženjerstvom površina sa primenom odgovarajućih prevlaka na površinama izloženim degradaciji. Tipična mikrostruktura prevlake za APS postupak je lamelarna u kojoj su prisutne mikropore, neistopljene čestice, međulamelarni oksidi i precipitati. Mehaničke karakteristike prevlake Cu10tež.%Al ispitane su merenjem mikrotvrdoće slojeva prevlake metodom HV0.3 i čvrstoće spoja metodom ispitivanja na zatezanje. Morfologija čestica praha i površina prevlake analizirana je na skening elektronskom mikroskopu (SEM). Analiza mikrostrukture prevlake urađena je uz korišćenje optičkog mikroskopa, a udeo mikropora određen je analizom mikrofotografija sa optičkog mikroskopa (OM).

For many years, huge attention has been paid to the problem of corrosion damage and destruction of metallic materials. Experience shows that failures due to corrosion problems are very important, and statistics at the world level shows that the damage resulting from the effects of various forms of corrosion is substantial and that, for example, in industrialized countries it reaches 4-5% of national incomes. Significant funds are determined annually for the prevention and control of corrosion. In the case of ignoring the problem of corrosion, in some cases the penalty is financial, whereas in other cases it is the loss of human lives. This review presents several cases of failures in engineering structures and installations of catastrophic proportions, where corrosion was responsible for the occurrence of failures and the loss of hundreds of lives. / Проблема разрушения металлических материалов вследсдтвие возникновения коррозии привлекает большое внимание уже долгие годы. Опыт показал, что отказы инженерных сетей в результате воздействия коррозии являются важной проблемой, а согласно статистике мирового уровня выявлено, что ущерб от воздействия коррозии в промышленно развитых странах составляет 4-5% национального дохода. В связи с данной проблемой, на годовом уровне выделяются средства на предупреждение и контроль коррозийного воздействия. Игнорирование опасности от коррозии влечет за собой финансовые потери, а в отдельных случаях и человеческие жертвы. В данной работе представлено несколько случаев масштабных отказов инженерных сетей и установок вследствие коррозийного воздействия, которые унесли сотни человеческих жизней. / Problemu korozivnog oštećenja i razaranja metalnih materijala već godinama se posvećuje velika pažnja. Svetska statistika pokazuje da je šteta koja nastaje usled delovanja različitih oblika korozije ogromna i da, na primer, u industrijski razvijenim zemljama dostiže 4 do 5% nacionalnog dohotka. Za prevenciju i kontrolu korozije izdvajaju se znatna sredstva na godišnjem nivou. U slučaju ignorisanja problema korozije izriču se finansijske kazne, a može doći i do katastrofalnih posledica – gubitka ljudskih života. U ovom članku predstavljeno je nekoliko slučajeva otkaza inženjerskih struktura i postrojenja katastrofalnih razmera, u kojima je korozija odgovorna za pojavu otkaza i pogibiju stotine ljudi.