Title Dugolančane organske kiseline kao inhibitori korozije čelika i legura bakra u prirodnim vodama Title (english) Longchain organic acids as corrosion inhibitors for steel and copper alloys in natural waters Author Ekatarina Kristan Mioč Mentor Helena Otmačić Ćurković (mentor)Committee member Sanja Martinez (predsjednik povjerenstva)Committee member Mirela Leskovac (član povjerenstva)Committee member Željka Petrović (član povjerenstva)Granter University of Zagreb Defense date and country 2018-11-08, Croatia Scientific / art field, TECHNICAL SCIENCES Universal decimal classificationUDC ) 66 - Chemical technology. Chemical and related industries Abstract Zaštita metalnih konstrukcija od korozije razvojem novih ekološki i ekonomski prihvatljivih metoda modificiranja površinskog sloja metala, jedan je od izazova današnjice. U tu svrhu, veliki potencijal primjene ima modificiranje metalne površine tankim uređenim filmovima organskih molekula, koji sprječavaju prodiranje vode i agresivnih iona do metalne površine. Iako su u posljednjim desetljećima organske kiseline, poput fosfonske i karboksilne, postale vrlo popularne za površinsku modifikaciju metalnih oksida u raznim područjima primjene, još uvijek nedostaju istraživanja o metodama pripreme reproducibilnih filmova na često korištenim legurama te o stabilnosti i trajnosti njihove zaštite u realnim uvjetima primjene.
Cilj ovog doktorskog rada je pronaći najpogodniju metodu formiranja uređenih i stabilnih samoorganizirajućih filmova dugolančanih fosfonskih i karboksilnih kiselina, na površini nehrđajućeg čelika AISI 316L te legure bakra i nikla, koji pružaju dobru zaštitu od korozije u prirodnim vodama. U tu svrhu korištene su tri metode nanošenja: metoda uranjanja, prskanja i elektrokemijska metoda, a za svaku od navedenih metoda utvrđivan je utjecaj parametara nanošenja, kao što su temperatura sušenja i adsorpcije, vrijeme sušenja i adsorpcije, potencijal nanošenja i dr., na svojstva dobivenog filma. Budući da je najvažnije svojstvo nastalih filmova korozijska zaštita, njihova temeljna karakterizacija provedena je elektrokemijskim tehnikama: polarizacijskim mjerenjima i elektrokemijskom impedancijskom spektroskopijom. Izabrani uzorci dodatno su karakterizirani spektroskopskim tehnikama (infracrvena i Ramanova spektroskopija), elektronskom i optičkom mikroskopijom, kao i goniometrijom. Na temelju svih rezultata za daljnja ispitivanja stabilnosti zaštitnih filmova u realnim uvjetima, odabrana je metoda prskanja oktadecil fosfonske kiseline zbog veće praktičnosti u potencijalnoj primjeni te vrlo visoke korozijske otpornosti u simuliranoj morskoj vodi. Ispitivanjem trajnosti dobivenih zaštita u protočnim uvjetima te praćenjem otpornosti na mikroorganizme elektrokemijskim tehnikama te analizom površine u prirodnim vodama, morskoj i riječnoj, utvrđeno je da filmovi oktadecil fosfonske kiseline pružaju dobru korozijsku zaštitu pri svim ispitivanim brzinama strujanja medija na obje ispitivane legure, pri čemu uspješno smanjuju i mogućnost pojave mikrobiološki uvjetovane korozije. Zadnjim korakom istraživanja ispitana je i mogućnost obnove zaštitnog filma in-situ.
Abstract (english) The corrosion protection of metallic structures by modification of their surface by using new, environmentally and economically acceptable methods is one of the challenges of modern industry. The application of thin, well-ordered films of organic molecules has a great potential in metal surface modification by preventing the penetration of water and aggressive ions towards the surface. While organic acids, such as phosphonic and carboxylic, have become popular surface modifiers for metal oxides in various fields, especially in the past decade, there is still a lack of consensus on deposition protocols, especially on alloys, as well as on their stability under realistic application condition. The aim of this thesis is to find the most suitable method of forming well-defined and stable self-assembled layers of longchain phosphonic and carboxylic acids on the surface of AISI 316L stainless steel and cupronickel alloy providing good corrosion protection in natural waters. Three preparation methods were used for this purpose: dip-coating, spraying and electrochemical method. For each method the influence of parameters, such as drying and adsorption temperature, drying and adsorption time, applied potential, etc., was examined. Since the most important feature of the obtained films is corrosion protection, their fundamental characterization was conducted by two electrochemical techniques: polarization measurements and electrochemical impedance spectroscopy. Selected samples were additionally characterized by spectroscopic techniques (infrared and Raman spectroscopy), electron and optical microscopy and goniometry. Based on these results, for testing of stability of the protective films in realistic conditions, the method of spraying octadecylphosphonic acid was selected, due to easier film formation and very high corrosion resistance observed in simulated seawater. After defining the optimal conditions for the film formation, the durability of such corrosion protection was tested in flow conditions. Also, the protection against microbially influenced corrosion in natural waters was studied by electrochemical techniques and the surface analysis. These measurements have shown that octadecylphosphonic acid films provide good corrosion protection at all tested media flow rates on both tested alloys, thereby successfully reducing the possibility of microbiogically infuenced corrosion. The last step of the research was to investigate the possibility of in-situ repair of the protective film.
Keywords
dugolančane organske kiseline
korozijska zaštita u prirodnim vodama
legura bakra i nikla
nehrđajući čelik
samoorganizirajući filmovi
Keywords (english)
longchain organic acids
corrosion protection in natural waters
cupronickel alloy
stainless steel
self-assembled layers
Language croatian URN:NBN urn:nbn:hr:149:938771 Promotion 2018 Project Number: 09.01/253 Study programme Title: Chemical Engineering and Applied Chemistry - Doctoral course Type of resource Text Extent 242 str. ; 30 cm File origin Born digital Access conditions Open access Terms of use Created on 2023-08-29 09:48:14
