As experts in the determination of the root cause failure of paints and coatings, our laboratories receive many technical enquiries. One commonly occurring enquiry which our laboratories receive concerns a galvanized coating failure on steel, or paint flaking and peeling on galvanized steel.
Our laboratories regularly receive galvanized components (unpainted and painted) from Quantity Surveyors and Façade Engineers, asking our chemists and engineers to elucidate why the galvanized coating is failing or why the paint applied to the galvanized coating, is failing.
The most common issue we see lies in the galvanizing process itself. In advance of the galvanizing step, the surface of the steel must be suitably prepared. Preparation involves several steps including degreasing and removing all rust. If this step has not been optimised, as the galvanized surface undergoes weathering, micro cracks will form in the zinc coating which will allow water to enter and further effect the adhesion of the zinc film to the steel surface.
Another matter which our laboratories are regularly asked to investigate, is the failure of powder coatings when applied to galvanized steel. If the galvanized surface is not absolutely dry before powder coating, during curing, the trapped water will push the powder coating off the galvanized surface, an in so doing, form unsightly fissures and blisters.
