AN INVESTIGATION INTO THE CORROSION BEHAVIOUR OF ZINC AND CHROMIUM METALLIC COATING ON MILD STEEL SUBSTRATE

An investigation into the corrosion behaviour of zinc and chromium metallic coating
on mild steel substrate is conducted. This is to show that using suitable coating is
good in preventing corrosion on mild steel. This project is also done to compare
which metallic coating is better for the mild steel substrate. The samples are grind
and polished before they are coated. The samples are coated with different period of
inunersion in plating bath to differ their coating thickness. Various tests are
conducted to compare the coating in different parameters. Salt spray test, linear
polarization measurement, hardness test, weight loss, surface roughness, and
inspection of microstructures of the coating together with substrate are done
according to ASTM standards. For this dissertation report, it is proven that adding
coating will enhance the mild steel hardness and appearance. It will also greatly
reduce the rate of corrosion of the mild steel substrate. With the increase thickness of
coating, the mild steel corrosion rate will be improved. The project also proved that
Chromium coating is superior to Zinc coating in terms of corrosion rate, hardness,
and surface roughness. It can also be concluded that corrosion will cause loss of
function and appearance towards the mild steel substrate such as decreased hardness
and also increased surface roughness.