Razvoj in analiza frit za emajliranje aluminijevih zlitin : doktorska disertacija

slovenian

doktorska dela

2021

3D profilometry   aluminium alloy   corrosion   electrochemistry   enamel   frit   ToF-SIMS   XPS

Univerza v Mariboru, Fakulteta za kemijo in kemijsko tehnologijo

The doctoral dissertation was based on the development of frit for enamelling aluminium alloys, as the use of alloys is increasing due to their low price, low density and excellent strength. Thus, alluminium alloys are used in various industries, but their use is limited due to their high chemical activity and potentially poor corrosion resistance in acidic, alkaline and chloride solutions. The study included research on various raw materials and the oxide composition of frit. In order to obtain a homogeneous granulate, the optimal time conditions and melting temperature were determined for each frit. The surface was observed with a heating microscope; moreover, the four melting points of the frits were determined: sintering, softening, half-sphere and melting. In addition, the thermal expansion coefficient of each frit was determined with a dilatometer and compared with the thermal expansion coefficient of the particular aluminium alloy.Prior to enamelling, alloy samples were cleaned and some were sanded to determine the effect of alloy preatreatment on enamel bonding. Several frits were prepared, of which seven were coated on three types of aluminium alloys: AA2024, AA6082, and AA7075. Optimal time conditions and the firing temperature were determined for each frit. The corrosion resistance of the coated samples was tested in a 5 wt. NaCl solution at room temperature using the electrochemical impedance spectroscopy and cyclic polarization measurements. The corrosion resistance of the enamelled samples increased compared to the respective noon-enamelled aluminium alloys. The composition, surface and depth homogeneity of the two most efficiently enamelled samples were confirmed using FE-SEM images, sputtering with an ion-surce clusters of argon and by the quantitative analysis using X-ray photoelectron spectroscopy. Additionally, the technique of mass spectrometry of secondary ions with a time-of-flight detector and sputtering using an O2+ source was used to describe the 3D composition of the frits. The depth of the formed crater was analyzed using a 3D profilometer.

07.08.2023