Once a primer or epoxy is on the steel, something has to protect it from sunlight. On architectural steel, water towers and exposed structures, that finish coat is also what the public sees. There are three main choices. Aliphatic polyurethane For decades the standard finish. Good gloss and color retention, applied at a thin film, reasonably priced and familiar to every applicator. Over time it chalks and fades. On a water tower carrying a town's name or a signature building

Galvanizing is itself a coating, so painting galvanized steel means coating a coating. Handrails, canopies, stair stringers and exposed structural steel on architectural projects are often galvanized, and paint peeling from them is a common callback. Why galvanized steel is difficult It is smooth and dense. There is no profile for the coating to grip. Zinc is reactive. Within days it begins forming zinc oxide and hydroxide, the white, powdery bloom known as white rust. That l

The floor looked perfect at the walkthrough. Six weeks later there are blisters the size of quarters. Cut one open and there is water inside. This is the most common concrete coating failure there is. Cause 1: Moisture vapor drive Blisters in a coated concrete floor almost always mean moisture coming up from below. A slab on grade sits on damp ground, and water vapor moves up through it constantly. Most high-performance epoxies have low permeability, which is good for protect

Much of what works on steel carries over to concrete. Much of it does not, and the part that does not is where most concrete coating failures start. Four ways concrete differs from steel It is porous. Concrete breathes and holds moisture. It is alkaline. Surface pH of 12 to 13 attacks some coatings from underneath. An alkyd applied to concrete turns soft and gummy because the alkali converts the oil binder into soap. It is weak in tension. Concrete cracks, and a rigid coating