A study of the influence of nanofiller additives on the performance of waterbourne primer coatings

Organic coatings are frequently applied to metals, often in circumstances where there is a need to protect the substrate from corrosion or to improve the aesthetic quality of a product. Increasingly, coatings are also expected to provide additional functionality, such as anti-bacterial properties. Concurrent with the need to satisfy ever more demanding specifications, coating formulators are being obliged to comply with stringent environmental legislation. A research area which may benefit the development of coating formulations is that of nanocomposite synthesis, in which the composite additives have at least one dimension in the nanometre size range. The current research has sought to modify a waterborne organic coating primer with two types of nano-sized additives: layered clays and titanium dioxide nanoparticles. Dispersion of the particles at loadings up to 5% w/w was achieved by ball milling and the modified coatings were subjected to numerous tests to ascertain the effect of the additives. Titanium dioxide was found to improve the tribological properties and corrosion resistance of the coatings, while the addition of magnesium aluminium hydroxycarbonate (hydrotalcite) layered clay had a deleterious effect. Some coatings exhibited a cracked morphology, although no correlation between particle loading and the presence of cracks could be determined. A preliminary investigation into substrate preparation was also conducted. This ensured that the degree of cleanliness of the hot-dip galvanized substrates was both satisfactory and consistent.