In areas where superior performance is required, powder coating applied over hot dip galvanized steel provides an additional surface barrier, encapsulating the cathodic protective zinc surface. The exterior and interior metal surface is hot dip galvanized in accordance with ASTM A-123. The exterior galvanized surface is washed under heat and pressure with an alkaline rinse to remove any excess oxides or contaminants. The exterior surface is then centrifugally brush blasted to remove excess oxides and foreign matter providing an anchor pattern profile. The blasted metal surface is chemically pretreated with an iron phosphate conversion coating forming a dry tight micro-crystalline coating. is a special powder coating formulated from a unique combination of polyester resins designed to exhibit superior outdoor weatherability, durability, and gloss retention, together with the galvanized surface to form a uniform bi-layer 8 mil coating. The internal galvanized section is coated with , a corrosion inhibitor, to form a protective internal barrier.