doktorski rad
One of the leading issues in industry and municipal infrastructure is the occurrence of corrosion damage, which poses a serious challenge due to its ability to cause significant financial losses and operational disruptions. This process not only reduces the lifespan of metal structures but also increases the costs of maintenance, repairs, and replacements, thereby directly impacting on the economic sustainability of projects. In response to this challenge, various surface protection methods have been developed that are based on isolating the metal surface from the aggressive environment through protective layers, which can be in the form of coatings, linings, or surface treatments.
This work focuses on corrosion protection of underground pipes, which are particularly exposed to aggressive conditions such as seawater and wastewater, microbiological environments, high humidity, and cyclic temperature changes. For this purpose, a multi-layer coating system made from chemically inert high-molecular polymeric materials containing epoxy groups is commonly used. Over the time, damage occurs to the epoxy coating, leading to the formation of micropores, microcracks, and swelling, making it necessary to further modify such organic coatings to extend the lifespan of the protection they provide.
To expand existing knowledge, this doctoral thesis investigates an active nanocomposite coating for the corrosion protection of drainage pipes. The examined system includes an epoxy matrix and fillers in the form of metal nanoparticles, whose role is to improve the coating's corrosion and microbiological resistance.
The experimental work is based on a series of input variables, which include the testing of different types and concentrations of metal nanoparticles, methods of their incorporation into the epoxy coating, and the interaction between the nanoparticles and the epoxy paint or pure epoxy resin. The effectiveness of the developed coatings was tested on a grey cast iron substrate. The addition of nanoparticles improved some of the key properties of the epoxy coating. The structural and morphological characteristics of the nanoparticles, unmodified epoxy coating, and nanocomposite coatings were determined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Based on the tested physical properties, it was found that the addition of nanoparticles improves one of the most critical parameters for coating durability, namely, the adhesion of the coating to the metal surface. Special attention was given to enhancing the anticorrosion and antibacterial properties of the modified coatings. For this purpose, three types of metal nanoparticles were used: aluminum, silver, and nickel. By using the electrochemical impedance spectroscopy, it was found that the nanocomposite coating containing 1% silver nanoparticles exhibits the best anticorrosive properties, followed by the nanocomposite coatings with nickel and aluminum. Additionally, the antibacterial properties of the epoxy coating and nanocomposite coatings were determined, revealing that the nanocomposite coatings with aluminum and silver yielded the best results, while the nanocomposite coating with nickel had minimal antibacterial activity. The nanocomposite with 1% aluminum nanoparticles showed significant migration, while the nanocomposites with silver and nickel nanoparticles exhibited the lowest migration values from the epoxy coating into wastewater. The amount of migrated aluminum nanoparticles initially increased gradually but reached a constant concentration of aluminum (1 mg/L) after 10 days of exposure to wastewater. The surface of the nanocomposite coating with 1% aluminum nanoparticles was analyzed by using the scanning electrochemical microscopy, and it was found that only these nanoparticles were capable of forming a passive oxide film on their surface, thus preventing the degradation of the coating. Therefore, samples modified with aluminum nanoparticles were tested in accelerated corrosion tests, including salt spray tests, high humidity conditions, and in a climate chamber.
Based on the conducted research, a nanocomposite coating containing aluminum nanoparticles was developed. These nanoparticles can migrate and oxidize in the event of corrosion or bacterial attack, thereby improving the corrosion and microbiological stability of the epoxy coating, with potential commercialization that could ultimately contribute to a longer lifespan of buried pipes.
antibacterial action; anticorrosive action; corrosion; epoxy coating; migration; nanoparticles
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