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Influence of temperature on elektrochemical and anomalous behaviour of chromium and chromium alloys in acid solutions

dc.contributor.advisorMaksimović, Miodrag D.
dc.contributor.otherGojković, Snežana Lj.
dc.contributor.otherPopić, Jovan P.
dc.creatorJegdić, Bore
dc.date.accessioned2016-01-05T12:42:58Z
dc.date.accessioned2019-02-04T12:07:57Z
dc.date.available2016-01-05T12:42:58Z
dc.date.available2019-02-04T12:07:57Z
dc.date.issued2008
dc.identifier.urihttp://eteze.bg.ac.rs/application/showtheses?thesesId=1132
dc.identifier.urihttps://fedorabg.bg.ac.rs/fedora/get/o:7896/bdef:Content/download
dc.identifier.urihttp://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=33904143
dc.identifier.urihttp://nardus.mpn.gov.rs/123456789/2940
dc.identifier.urihttp://cer.ihtm.bg.ac.rs/handle/123456789/2545
dc.description.abstractIspitivan je uticaj temperature na elektrohemijsko i hemijsko rastvaranje tri vrste hroma u neutralnim i kiselim rastvorima sulfata, sa i bez dodatka hloridnih jona (krupnozrni liveni hrom, sitnozrni valjani hrom i prevlaka hroma). Takođe su ispitivane elektrohemijske i korozione karakteristike nerđajućeg čelika 304 (18Cr-9Ni).Brzine elektrohemijske i hemijske korozije su međusobno slične kod sve tri vrste hroma, iako prevlaka hroma ima 5 puta bržu anodnu reakciju i skoro 5 puta sporiju katodnu reakciju izdvajanja vodonika. Hrom sa teksturom (110) je manje elektrohemijski aktivan (anodno i katodno) u odnosu na hrom sa teksturom (111). Kristalna ravan (110) je najgušće pakovana ravan kod hroma.Reakcije izdvajanja vodonika, anodnog rastvaranja i hemijskog rastvaranja hroma sa aktivirane površine hroma u rastvoru sumporne kiseline pH 1 slede Arenijusovu zavisnost sa prividnom energijom aktivacije 35 kJ mol-1, 58 kJ mol-1 i 62 kJ mol-1, respektivno. Veća energija aktivacije za anodni proces, nego za katodni, dovela je do pomeranja korozionog potencijala u smeru negativnih potencijala za približno 0,8 mV K-1. Velika energija aktivacije hemijskog rastvaranja hroma dovodi na povišenim temperaturama do znatno izraženije hemijske korozije u odnosu na elektrohemijsku koroziju.Pri koncentracijama Cl- jona manjim od 3 M, korozioni potencijal je posledica simultanog odvijanja reakcije izdvajanja vodonika na oksidom prekrivenoj površini hroma sa reakcijom anodnog rastvaranja hroma kroz pasivni film (Ekor.1) ili katodnim izdvajanjem vodonika i anodnim rastvaranjem ogoljene površine kada se površina hroma depasivira (Ekor.2). Za koncentracije Cl- jona veće od 3,5 M površina pasivnog hroma se spontano aktivira i tada se primećuje samo jedan korozioni potencijal Ekor.2.Primećeni anodni pik na elektrodama od nerđajućeg čelika 304 u sumpornoj kiselini nije realni anodni pasivacioni pik, kao što je primećeno za veći broj metala u sličnim uslovima, već potiče od anodne oksidacije vodonika apsorbovanog tokom katodne polarizacije. Ukupna anodna gustina struje na potencijalu otvorenog kola je suma anodne pasivacione struje i odgovarajuće struje oksidacije apsorbovanog vodonika, tako da korozioni potencijal postaje pozitivniji kako se smanjuje koncentracija apsorbovanog vodonika i jH → 0. Katodno izdvajanje vodonika se odvija na pasivnom filmu. Korozioni potencijal elektrode od čelika 304 koji nije bio zasićen vodonikom je potencijal koji se formira u saglasnosti sa elektrohemijskim Vagner-Traudovim modelom sa dve suprotne reakcije (katodno izdvajanje vodonika na pasiviranom čeliku i anodno rastvaranje metala kroz pasivni film). Katodnom aktivacijom i dugotrajnijom katodnom polarizacijom do značajno negativnih potencijala i vrlo velikih katodnih struja nije bilo moguće da se pasivni sloj ukloni i postigne aktivno elektrohemijsko rastvaranja metala bez prisustva pasivnog sloja, tj. da se dobije slobodna metalna površina.sr
dc.description.abstractThe influence of temperature on electrochemical and chemical dissolution of three types of chromium (cast chromium, metallic fine-grained chromium, and electroplated coating of chromium on steel coupons) was studied in neutral and acidic sulphuric solutions, with and without the addition of chloride ions. Also, electrochemical and corrosion characteristics of the stainless steel 304 (18Cr-9Ni) electrode were studied.The electrochemical and chemical corrosion rate of all types of chromium was similar, although chromium coating has 5 times faster anodic reaction, and almost 5 times slower hydrogen evolution cathodic reaction. The chromium with texture (110) was somewhat less active electrochemically (both anodic and cathodic), than the chromium with texture (111). Crystalline plane (110) is the most dense packed chromium plane.The hydrogen evolution reaction, as well as the anodic dissolution and chemical dissolution of chromium from activated surfaces in sulphuric acid solutions pH 1 follows Arrhenius law, with the apparent activation energies of 35 kJ mol-1, 58 kJ mol-1 and 62 kJ mol-1, respectively. The higher activation energy for the anodic process, than for the cathodic one resulted in shifting of corrosion potential in the negative direction for approximately 0.8 mV K-1. The higher activation energy for chemical dissolution than for the electrochemical chromium corrosion at higher temperatures increases considerably the part of chemical corrosion in the overall corrosion of chromium.When the concentration of Cl- ions is smaller than 3 M, corrosion potential is the result of simultaneous cathodic reaction of hydrogen evolution on chromium oxide covered surface and anodic dissolution of chromium through the passive film (Ecorr.1), or by the cathodic hydrogen evolution and anodic dissolution on bare chromium, when the chromium surface is activated (Ecorr.2). When the concentration of Cl- ions is higher than 3.5 M, the passive chromium surface is immediately activated, and then only one corrosion potential Ecorr.2 can be noticed.The observed anodic peak on the anodic potentiodynamic curve for 304 stainless steel electrode in deaerated sulphuric acid solutions appears not to be the real anodic passivation peak, as it was observed for a number of metals in similar conditions, but peak which arises from the anodic oxidation of hydrogen absorbed during previous cathodic polarization. The total anodic current density at the open circuit potential is the sum of the anodic passivation current density and the corresponding anodic current density for the oxidation of the previously absorbed hydrogen, so that the corrosion potential becomes positive as the absorbed hydrogen concentration decreases and jH → 0. The cathodic reaction of hydrogen evolution is occurring on the stainless steel surface with a passive film.Corrosion potential (for 304 stainless steel electrode without absorbed hydrogen) is established according to the electrochemical Vagner-Traud model, with two opposite reactions: cathodic reaction of hydrogen dissolution on a passive surface of steel and an anodic reaction of dissolution of metal through a passive film. It was impossible to remove a passive film and starts the active electrochemical dissolution without the passive layer, i.e. at a bare metallic surface, with the cathodic activation or a longer cathodic polarization to more negative potentials.en
dc.formatapplication/pdf
dc.languagesr
dc.publisherУниверзитет у Београду, Технолошко-металуршки факултетsr
dc.rightsopenAccess
dc.sourceУниверзитет у Београдуsr
dc.subjecthrom, nerđajući čelici, hemijsko rastvaranje hroma, energija aktivacije, korozioni potencijal, korozija nerđajućih čelikasr
dc.subjectchromium, stainless steels, chemical dissolution of chromium, activation energy, corrosion potential, corrosion of stainless steelsen
dc.titleUticaj temperature na elektrohemijsko i anomalno ponašanje hroma i legura hroma u kiselim sredinamasr
dc.titleInfluence of temperature on elektrochemical and anomalous behaviour of chromium and chromium alloys in acid solutionsen
dc.typedoctoralThesisen
dc.rights.licenseBY-NC-ND
dcterms.abstractМаксимовић, Миодраг; Гојковић, Снежана; Попић, Јован П.; Јегдић, Боре В.; Утицај температуре на електрохемијско и аномално понашање хрома и легура хрома у киселим срединама; Утицај температуре на електрохемијско и аномално понашање хрома и легура хрома у киселим срединама;
dc.identifier.fulltexthttp://cer.ihtm.bg.ac.rs/bitstream/id/5781/Disertacija.pdf
dc.type.versionpublishedVersion


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