Modifikacija hrđe formiranjem zaštitnog sloja netoksičnih korozijskih inhibitora na čeliku

master's thesis

• Title (english): Rust modification by formation of protective layer of nontoxic corrosion inhibitors on steel
• Author: Ana Kraš
• Mentor: Sanja Martinez (mentor)
• Committee member: Sanja Martinez (predsjednik povjerenstva)
• Committee member: Zoran Mandić (član povjerenstva)
• Committee member: Davor Dolar (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2019-07-11, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry

Abstract

U ovom radu istraživana je mogućnosti formiranja modificiranog sloja hrđe kombinacijom različitih prirodnih, netoksičnih korozijskih inhibitora s kestenovim taninom, kao temeljnim inhibitorom. Ostali ispitivani inhibitori bili su škrob, polietilen glikol (PEG 400), heksamin i propolis. Vizualna inspekcija nastalih slojeva odabrana je kao početni evaluacijski parametar kvalitete sloja s ciljem dobivanja optimalne koncentracije i vrste inhibitora: tanin koncentracije 300 mg dm^-3 (T300) u sinergizmu s propolisom koncentracije 80 mg dm^-3 (P80) formira sloj najboljeg izgleda. Uz vizualno praćenje, kvaliteta optimiziranog sloja potvrđena je SEM i FTIR analizom, koje upućuju na modificiranost sloja hrđe nastalim željezovim tanatima. Podrobniji uvid u svojstva inhibitora dobiven je elektrokemijskim metodama u 3,5% NaCl-u. Rezultati elektrokemijske impedancijske spektroskopije donekle idu u prilog pozitivnom efektu kombinacije P80+T300, dok konačnu potvrdu zaštitnih svojstava daju rezultati polarizacijskih krivulja. Povećana brzina miješanja prilikom mjerenja polarizacijskih krivulja P80+T300 dovodi do pomaka korozijskog potencijala u negativnom smjeru, što upućuje na katodno djelovanje inhibitorskog sloja kao barijere difuziji kisika s visokom otpornosti na protok elektrolita. Maksimum inhibicijske efikasnosti postiže se pri brzini miješanja 1000 r min^-1 te iznosi 73,71% u odnosu na sloj hrđe, tj. 73,35% u odnosu na čisti kupon ugljičnog čelika. Time je pronađena i potencijalna primjena dobivenih svojstava zaštitnog sloja – u protočnim sustavima s aeriranom vodovodnom ili slanom vodom.

Abstract (english)

This paper investigated the possibility of forming a modified rust layer by combining various natural, non-toxic corrosion inhibitors with chestnut tannin as the basic inhibitor. Other investigated inhibitors were starch, polyethylene glycol (PEG 400), propolis and hexamine. The visual inspection of the formed layers was selected as the initial evaluation parameter in order to obtain an optimum concentration, as well as the type of inhibitor: 300 mg dm^-3 tannin concentration (T300) in synergism with the 80 mg dm^-3 propolis concertation (P80) creates a layer with the best appearance. The quality of the optimized layer was further confirmed with SEM and FTIR analysis, suggesting the modification of the rust layer by formation of iron tannate. More detailed insight into inhibitory properties was obtained by electrochemical methods in 3.5% NaCl solutions. The results obtained by electrochemical impedance spectroscopy (EIS) somewhat favor the use of the combination P80 + T300, but the final confirmation of the protective properties is definitely given in the polarization curves. Increasing mixing rate during measurements of the P80 + T300 leads to a negative shift of the corrosion potential, indicating the cathodic behavior of the protective layer as an oxygen diffusion barrier of high electrolyte resistance. Maximum inhibition efficiency was obtained at 1000 r min^-1 and equals 73.71% with respect to the rust layer and 73.35% with respect to the pure carbon steel. Thus, the potential application of the protective layer properties was found to be in systems of flowing aerated water or salt water.

• Keywords: korozijski inhibitor; vizualna inspekcija; tanin; propolis; sinergizam
• Keywords (english): corrosion inhibitor; visual inspection; tannin; propolis; synergism
• Language: croatian
• URN:NBN: urn:nbn:hr:149:018203
• Study programme: Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry; Course: Advanced materials and technologies; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra primijenjene kemije (magistar/magistra primijenjene kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Access restricted to students and staff of home institution
• Created on: 2022-02-22 12:25:20