Zinc coatings stop rusting of the confined metal by creating a physical blockage, and by acting as a sacrificial anode even if this obtruction is spoiled. As soon as uncovered to the atmosphere, zinc act in response with oxygen to form zinc oxide, which additionally respond with water molecules in the air to make zinc hydroxide. consecutively, zinc hydroxide reacts with carbon dioxide in the enviroment to produce a thin, waterproof, firm and extremely impenetrable faded gray layer of zinc carbonate which adheres tremendously well to the underlying zinc, so defending it from getting rusty. This is comparable to the sheild afforded to aluminium and stainless steels by their oxide layers.
Hot-dip galvanizing build up a dense tough layer that may be more than is needed for the protection of the orginal metal in few applications. This is the scenerio in automobile bodies, where extra rust proofing paint will be applied. This is a consideration for the manufacture of Galvanized Wire and other highly-stressed products. Galvanized Wire protection is insufficient for products that will be frequently exposed to acidic materials such as salt water. For these, more costly stainless steel is would be prefered.
