|
An important approach to rust prevention entails galvanization, which typically consists of an application, on the object to be protected, of a layer of zinc by either hot-dip galvanizing or electroplating. Zinc is traditionally used because it is cheap, adheres well to steel and provides a cathodic protection to the steel surface in case of damage of the Zinc layer. In more corrosive environments (such as salt water) cadmium is preferred. Galvanization often fails at seams, holes, and joints, where the coating is pierced. In these cases the coating provides cathodic protection to metal, where it acts as a galvanic anode rusting in preference. More modern coatings add aluminium to the coating as zinc-alume, aluminium will migrate to cover scratches and thus provide protection for longer. These approaches rely on the aluminium and zinc oxides protecting the once-scratched surface rather than oxidizing as a sacrificial anode. In some cases, very aggressive environments or long design life, both zinc and a coating are applied to provide corrosion protection.
www.ruscontrolchemicals.com
|