Hot Dip Galvanizing is the process of dipping a fabricated metal product into a vat of molten zinc. While immersed, the zinc forms a metallurgic bond with the metal product, providing an additional layer of protection from corrosion and other forms of environmental abrasion. As the zinc coating weathers it forms a zinc patina which provides an additional layer of corrosion protection. The cost of corrosion is estimated to cost an industrialized country at least 5% of its GDP per year. A hot dipped galvanized product is estimated to last 40 years depending on whether the initial process was done correctly and as well as other environmental factors.
Q : How Does Galvanizing Protect Steel From Corrosion?
A : Zinc metal used in the galvanizing process provides an impervious barrier between the steel substrate and corrosive elements in the atmosphere. It does not allow moisture and corrosive chlorides and sulfides to attack the steel. Zinc is more importantly anodic to steel – meaning it will corrode before the steel, until the zinc is entirely consumed.
Q : How Long Does HDG Lasts?
A : Hot Dipped Galvanizing (HDG) is often used to protect steel from corrosion in some of the harshes environments imaginable, yet it provides maintenance-free longevity for decades. The corrosion resistence of HDG varies according to its surroundings, but generally corrodes at a rate of 1/30 of bare steel in the same environment. The corrosion resistance of zinc coatins is determined primarily by the thickness of the coating but varies with the severity of environmental conditions. Each environment affects HDG differently based on a unique set of corrosion variables.
Q : What are the specifications governing HDG?
A : Structural steel (plates, beams, angles, channels, pipe, tubing) are galvanized to ASTM A123/A123M. Fasteners and small parts that fit into a centrifuging basket are galvanized ASTM A 153/A 153M. Reinforcing steel is galvanized to ASTM A 767/A 767M.
Q : What are the size limitations of steel that is to be galvanized?
A : Our zinc coating VAT can handle up to dimensionsof 20 FT (L) X 4 FT(W) X 4FT(D)
Q : Can I paint right over the galvanized coating?
A : Galvanized coatings can be easily and effectively painted, not only for aesthetics but also to extend the structure’s service life. The age and extent of weathering of the galvanized coating dictate the extent of surface preparation required to produce a quality paint system over galvanized steel. ASTM D 6386, Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting, should be consulted for suggested surface preparation methods for galvanized coatings of varying ages.
Q : Is the zinc coating’s thickness consistent over the entire piece?
A : Coating thickness depends on the thickness, roughness, chemistry, and design of the steel being galvanized. Any or all of these factors could produce galvanized coatings of non-uniform thickness.