Utjecaj medija i mikrostrukture na korozijsko ponašanje sivog lijeva

Scientific paper - Original scientific paper

• Title (english): Influence of medium and microstructure on corrosion behavior of gray cast iron
• Author: Anita Begić Hadžipašić
• Author: Sandra Brajčinović
• Author: Gordana Gojsević Marić
• Author: Zdenka Zovko Brodarac
• Editor: Natalija Dolić
• Editor: Zdenka Zovko Brodarac
• Editor: Anita Begić Hadžipašić
• Author's institution: University of Zagreb; Faculty of Metallurgy
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy

Abstract (croatian)

U ovom radu ispitana je korozijska otpornost sivog lijeva u mediju umjetne kiše i mediju 0,5 M H2SO4 te utjecaj mikostrukture na njegovo korozijsko ponašanje u navedenim medijima. Tafelovom ekstrapolacijom polarizacijskih krivulja je ustanovljeno da ispitani sivi lijev pokazuje izrazito veliku brzinu korozije u kiselom mediju za razliku od ispitivanja u mediju umjetne kiše, gdje brzina korozije poprima znatno manju vrijednost. Međutim, u usporedbi s rezultatima ranijih istraživanja dobivenim za nodularni lijev te su vrijednosti trostruko vede, što upuduje na činjenicu da je nodularni lijev ipak korozijski otporniji u uvjetima atmosferske korozije te stoga i prihvatljiviji za izradu dijelova za poljoprivredne strojeve. Dobiveni rezultati su potvrđeni i metodom elektrokemijske impedancijske spektroskopije, pri čemu je u mediju umjetne kiše za sivi lijev registriran manji otpor prijenosu naboja od nodularnog lijeva. To ukazuje na činjenicu da se na sivom lijevu formirao tanji sloj, koji predstavlja slabu barijeru prema prodiranju agresivnih iona iz otopine. Dobiveno korozijsko ponašanje sivog lijeva u ispitanim medijima može se povezati i s njegovom mikrostrukturom. Naime agresivni ioni iz primijenjenih medija napadaju metalnu osnovu ispitanih materijala, dok grafit zadržava svoj prvobitni oblik. Pri usporedbi s nodularnim lijevom, nodule su se pokazale kao povoljniji oblik izlučenog grafita jer bolje prekrivaju površinu uzorka i slijedom navedenog izoliraju uzorak u procesu elektrokemijske korozije.

Abstract (english)

This paper investigated the corrosion resistance of gray cast iron in the medium of artificial rain and 0.5 M H2SO4 medium and the effect of microstructure on its corrosion behavior in the mentioned media. By Tafel's extrapolation of the polarization curves, it was found that the examined gray cast iron shows an extremely high corrosion rate in the acidic medium, as opposed to the artificial rain test, where the corrosion rate is much lower. However, compared with the results of earlier researches obtained for nodular cast iron these values are three times higher, indicating that the nodular cast iron is more corrosion-resistant to atmospheric corrosion and therefore more acceptable for the manufacture of parts for agricultural machines. The obtained results were confirmed by the method of electrochemical impedance spectroscopy, where in the medium of artificial rain lower value of charge transfer resistance of gray cast iron was registered in opposite to nodular cast iron. These points to the fact that a thin layer formed on the gray cast iron, which represents a weak barrier to penetrating aggressive ions from the solution. The corrosion behavior of the gray cast iron in the tested media can also be related to its microstructure. Namely, aggressive ions from the applied media attack the metal matrix of the examined materials, while the graphite retains its original form. When compared to nodular cast iron, the nodules seems to be a more favorable form of precipitated graphite due to better sample surface covering and therefore the insulation in electrochemical corrosion process.

• Keywords (croatian): sivi lijev, brzina korozije, impedancija, umjetna kiša, mikrostruktura
• Keywords (english): gray cast iron, corrosion rate, impedance, artificial rain, microstructure
• Language: croatian
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Publication title: Proceedings Book 17th International Foundrymen Conference Hi-tech casting solution and knowledge based engineering
• Numbering: pp. 98-112
• ISBN: 978-953-7082-31-4
• URN:NBN: urn:nbn:hr:115:877019
• Publication: 2018
• Conference: Title: 17th International Foundrymen Conference; Location: Opatija, Croatia; Start date: 2018-05-16; End date: 2018-05-18; Assembly type: Lecture
• Type of resource: Text
• Publisher: Sveučilište u Zagrebu Metalurški fakultet
• Publishing place: Sisak
• Access conditions: Open access
• Created on: 2019-04-24 06:01:48