Title Razvoj metode procjene zaštitnih svojstava premaza za primjenu u ekstremno korozivnom okolišu Title (english) The development of a method for the protective properties evaluation of the coatings for application in extremely corrosive environment Author Marina Mrđa Lalić Mentor Sanja Martinez (mentor)Committee member Helena Otmačić Ćurković (predsjednik povjerenstva)Committee member Mirela Leskovac (član povjerenstva)Committee member Ivan Stojanović (član povjerenstva)Granter University of Zagreb Defense date and country 2019-12-17, Croatia Scientific / art field, TECHNICAL SCIENCES Universal decimal classificationUDC ) 66 - Chemical technology. Chemical and related industries Abstract Primjena premaza najčešći je oblik zaštite čelika od korozije. Izbor premaza za zaštitu od korozije ovisi o razini korozivnog okoliša u kojem će se nalaziti i potrebnom vijeku trajanja. Dobro odabran sustav zaštite smanjit će troškove održavanja i osigurati zaštitu od korozije tijekom predviđenog životnog vijeka konstrukcije. Sustavi premaza od kojih se očekuje trajnost duži vremenski period u ekstremno korozivnom okruženju često ne prolaze odgovarajuća ispitivanja propisana međunarodnim normama zbog njihove vremenske i financijske zahtjevnosti. Prema istim normama, ocjena premaza provodi se na kraju perioda izlaganja ubrzanom korozijskom djelovanju u komorama vizualnim putem, podložnim subjektivnoj procjeni, te mjerenjima prionjivosti koja imaju veliku mjernu nesigurnost. Svrha ovog rada bila je unaprjeđenje procjene trajnosti sustava premaza primjenom metode elektrokemijske impedancijske spektroskopije (EIS) koja omogućuje kontinuirano praćenje kvalitete premaza te kvantifikaciju kvalitete kroz parametar modula impedancije. Ispitivani su različiti sustavi premaza poznate očekivane trajnosti u skladu s normom ISO 12944. Po prvi put je u svrhu kontinuiranog praćenja impedancije uzoraka izloženih u komori primijenjen inovativni sklop s ćelijom u obliku dvije elektrode i gel elektrolitom. Za usporedbu, rađena su ispitivanja i EIS metodom u mjernoj ćeliji s tekućim elektrolitom izrađenoj prema normi ISO 16773-2. Pokazano je da navedenim metodama moguće detektirati vrlo male razlike u svojstvima visokokvalitetnih sustava premaza čija je impedancija >10^10 Ω te da je moguće pratiti gubitak zaštitnih svojstava premaza koji je kod lošijih premaza karakteriziran padom impedancije ispod 10^6 Ω i prije pojave vizualnih promjena na površini premaza. Stanje premaza prije i poslije izlaganja u komori karakterizirano je i komplementarnim metodama analize FTIR, DSC, TGA, mjerenjima površinske napetosti i prionjivosti te je analizirana korelacija s EIS metodom. Kao zaključak rada, predložena je nova metodologija kontinuiranog praćenja impedancije premaza mjernim sklopom s fleksibilnim elektrodama i gel elektrolitom tijekom izlaganja u komorama. Metodologija predstavlja značajno unaprjeđenje, posebice kod premaza visoke trajnosti jer omogućava ocjenu impedancije u prvih 100 h izlaganja prije vizualno zamjetne degradacije, što može donijeti značajnu uštedu u troškovima ispitivanja i kasnijim troškovima održavanja.
Abstract (english) Coatings are the most common form of corrosion protection for steel. The choice of a coating system depends on the corrosive environment in which it will be exposed and the required service life. A well-chosen protection system will reduce maintenance costs and provide corrosion protection over the intended construction lifetime. Coating systems that are expected to last for a long period of time in extremely corrosive environments often do not pass the appropriate tests prescribed by international standards because of their length and financial requirements. The assessment of coatings is carried out at the end of the period of exposure to accelerated corrosion tests in the chambers by visual means, that are prone to subjective evaluation, and adhesion measurements, which have high measurement uncertainty. The purpose of this paper was to improve the assessment of the durability by the use of electrochemical impedance spectroscopy (EIS), which enables continuous monitoring and quantification of coating quality through the impedance modulus. Different coating systems of known expected durability were tested in accordance with standard ISO 12944. For the first time, for the purpose of continuous monitoring of the impedance of the samples exposed in the chamber, an innovative setup with a cell in the form of two electrodes and a gel electrolyte was applied. For comparison, tests were also performed in a liquid electrolyte measuring cell made according to ISO 16773-2. Very small differences in the properties of high-quality coating systems whose impedance is > 10^10 Ω could be detected. Also, the loss of the protective properties of the coating was measured, which in poor coatings is characterized by a drop-in impedance below 10^6 Ω before the appearance of visual changes on the surface of the coating. The condition of the coatings before and after exposure in the chamber was also characterized FTIR, DSC, TGA analysis methods, surface tension and adhesion measurements, and correlation with the EIS method was analyzed. As a conclusion of the thesis, a new methodology for continuous monitoring of the coating impedance is proposed by using the assembly with flexible electrodes and gel electrolyte during exposure in chambers. The methodology presents a significant improvement, especially with high durability coatings, as it provides an impedance rating in the first 100 h of exposure before visually noticeable degradation, which can result in significant savings in test and subsequent maintenance costs.
Keywords
trajnost premaza
EIS
slana komora
degradacija premaza
Keywords (english)
durability of coating
EIS
salt spray chamber
coating degradation
Language croatian URN:NBN urn:nbn:hr:149:785980 Promotion 2019 Study programme Title: Chemical Engineering and Applied Chemistry - Doctoral course Type of resource Text Extent 153 str. : 30 cm File origin Born digital Access conditions Access restricted to students and staff of home institution Terms of use Created on 2023-08-28 11:05:48
