Hot dip galvanized steel will last very well in most environments. It is not uncommon for galvanized steel to last more than 70 years under certain conditions.
The three intermetallic layers that form during the galvanizing process are all harder than the substrate steel and have excellent abrasion resistance.
“White Rust” or wet storage stain is formed because, zinc on newly galvanized steel is very reactive and quickly forms zinc oxide and zinc hydroxide corrosion products that go on to become the stable zinc carbonate.
When galvanized steel is stacked damp, stored in wet boxes, or shrink wrapped with no free flowing air, the zinc forms excessive layers of zinc hydroxide, otherwise known as wet storage stain. Most wet storage stain can be easily removed with a nylon brush. To prevent wet storage stain, store galvanized steel indoors and in such a way to allow free flowing air between each galvanized item.
The chemistry of the steel is the main influence on coating thickness and appearance. Steel produced by the steel companies has a wide variety of chemistries, thus the different coating appearances. The galvanizer may also add several different additives to their galvanizing bath to enhance the coating appearance by making it shiny, spangled or minimizing the reactivity of certain steel chemistries. The appearance of the coating does not change the corrosion protection of the zinc coating.
Depending on the product and condition of the steel surface, the initial cost of galvanizing can be the same as a good quality paint system. However when the lifetime cost of a project is considered, galvanizing can give you up to 60 years maintenance free, whereas paint systems will require maintenance or reapplication at various intervals over their lifetime, meaning costs can be considerable in the long run.
Hot-dip fasteners generally have about 10 times as much zinc on the surface and are suitable for use in all exterior and interior applications. Zinc-plated fasteners will provide a disappointing performance if used outside, especially when used to connect hot-dip galvanized structural steel.
The main reason for these holes is to allow otherwise trapped air and gases to escape, and to allow cleaning chemicals and molten zinc metal to flow throughout the fabrication, and then back into the tank. Because of the temperatures involved in the galvanizing process there is a significant risk of explosion when any trapped liquid is rapidly heated in the galvanizing bath.
Your local Galvanizing plant will be able to provide free technical advice on venting and drainage to give you the best possible finish.
There is no such thing as cold galvanizing. The term is often used in reference to painting with zinc-rich paint. Galvanizing requires heat in order to produce the metallurgical bond between coating and steel that gives galvanizing its long life and hard wearing characteristics.
