Manufacture and Characterization of Geopolymer Coatings Deposited from Suspensions on Aluminium Substrates

Abstract

Geopolymers compete with a number of conventional coatings and a few of them have already been replaced. The aim of this work was the analysis of alkali-activated metakaolin-based geopolymers and their use as brush-applied coatings, which were chosen due to their simplicity and cost-effectiveness. Eight coatings were prepared and the AlMgSi aluminum alloy underlying the substrate was also studied. The main characterizations of the prepared coatings were the microscopy analysis, which showed that manual painting with a brush on the coatings we prepared could achieve a high-quality geopolymer layer, and that if microscopic cracks are visible on the surface, they are uniform and do not affect the resulting cohesiveness of the coating. The thicknesses of these coatings are different, ranging from 1.5 to 11 μm, with no visible anomalies. For the evaluation of the properties of the coatings, we determined the analysis of adhesion to the adjacent substrate, microhardness and thermal expansion determined using the so-called dilatometric analysis as important criteria. For these analyses, the results vary by geopolymer type and are discussed in the following chapters.