Preparation and characterization of multilayered films withchemical corrosion resistance

In recent years, the development of thin films with controllable properties to enhance functionality of surfaces has become a widespread research topic, preferred for applications in separation processes, biotechnology, and surface coatings designed to protect surfaces from various hazards like corrosion. In this context, the Layer-by-Layer (LbL) coating method, which is economical and relatively simple to apply, is a widely used technique for producing thin films. Nowadays, with the development of the petrochemical, marine, aviation, and automotive industries, the economic losses caused by corrosion have become critical, and LbL multilayer films have also gained interest for corrosion protection. In this thesis, chemical corrosion-resistant multilayer functional films (PEM) have been prepared from polyelectrolytes (PEs) and benzotriazole (BTA) and/or imidazolium-based ionic liquid (IL), which have been extensively studied for their anticorrosive properties using Quartz Crystal Microbalance with Dissipation (QCM-D) technique considering two different approaches. In the first approach, the accumulation of corrosion inhibitors, individually passed over the surfaces of the freshly prepared respective PEMs, was examined, and the weight and viscoelastic changes within the PEM structure were monitored. In the second approach, the inhibitors used, being positively charged at suitable pH, were directly added into the cationic PE to design LbL film including anticorrosive agent during multilayer grow up. According to the findings obtained from QCM-D studies, Fourier Transform Infrared Spectroscopy (FTIR) and UV-VIS Spectroscopy (UV-VIS) analyses were conducted to confirm the presence of inhibitors in the (PAH.BTA-PAA)5, (PAH.IL0.8-PAA)5, and (PAH.IL.BTA-PAA)5 film, which exhibited the highest mass adsorption on the QCM-D sensor surface. Additionally, surface contact angle measurements and optical microscope analysis were conducted to examine the surface characterizations of the films while Open Circuit Potential (OCP), Tafel, Potentiodynamic Polarization, and Electrochemical Impedance Spectroscopy (EIS) measurements were performed to investigate their electrochemical properties. In this thesis, (PAH.BTA-PAA)50, (PAH.IL0.8-PAA)50, and (PAH.IL.BTA-PAA)50 PEM structures provided effective corrosion protection on the AA2024 aluminum alloy used as a substrate. Among the prepared PEMs, (PAH.IL.BTA-PAA)50 exhibited higher corrosion protection performance with a corrosion rate approximately 10 times slower than that of the AA2024 sample. As a result, multilayered functional thin films with varying compositions depending on the type of PE and corrosion inhibitor used in the thesis have been successfully prepared, and their layer build up have been examined using QCM-D technique. Electrochemical analysis showed that these films obviously displayed chemical corrosion resistance. The obtained results are expected to contribute to the scientific literature, especially because of the lack of similar study using QCM-D technique and superior corrosion protection performance of IL-BTA mixture used as a corrosion inhibition agent due to its synergistic effect.