How Are Galvanized Steel Posts Made?
In the construction industry, galvanized steel posts have many benefits. As well as being ultra-strong, durable and resistant to damage, galvanized steel posts have a longer life expectancy than stainless steel and are cheaper to manufacture.
What Is Galvanized Steel?
Galvanized steel posts consist of carbon steel that is coated in zinc. This zinc coating prevents corrosion, thus prolonging the life of the steel.
How Is Steel Galvanized?
There are several different galvanization methods, but the main approach used to produce galvanized steel posts is Hot-Dip Galvanization.
In order to produce galvanized steel posts by hot-dip galvanization, the posts must first go through a cleaning procedure known as Surface Preparation. This involves a three step process of degreasing, pickling and fluxing the steel post. Degreasing removes any dirt, oil or organic impurities. Pickling eliminates traces of iron oxide and mill scale. Fluxing removes any leftover oxides and prevents further oxidization prior to galvanization. This cleaning process may seem excessive, but it is vital because zinc will not react with unclean steel, meaning the post will not be galvanized effectively if it contains impurities.
After all contaminants have been removed, the posts are immersed in molten zinc. This coats the entire surface of the columns. The amount of zinc and zinc-alloy coating used is governed by the mass of the post that is being galvanized. However, regardless of mass or size, there is a standard minimum coating thickness which is applied automatically. The corners and edges of the post will have a thicker layer of galvanization, giving added durability to the weaker points of the galvanized steel posts.
Once a galvanized steel post is formed, it is then visually inspected. As mentioned earlier, zinc doesn’t react with steel if there are impurities present. This means that any problems will be immediately obvious by uncoated spots on the post. Along with this visual inspection, the thickness of the zinc coating is measured using a magnetic thickness gauge. This ensures that the coating complies with the regulatory coating thickness.
How Is the Zinc Coating So Strong?
The zinc coating has a strength of 3,600psi, and because the zinc-iron alloy layers are harder than the underlying steel, they offer maximum fortification. Studies have shown that the coating offers protection even when it has been damaged.
If the galvanized steel post will be placed in close contact with copper or brass in a humid environment, there is a chance that the zinc coating will corrode rapidly. This is due to a chemical reaction known as bimetallic corrosion, where two metals of different galvanic status react against each other. The anodic metal, which in this case is the galvanized steel post, is attacked and begins to corrode quickly. The reaction is so strong that it can even be caused by runoff water from copper or brass surfaces.
Great care should be taken in the design of the construction to ensure that galvanized steel posts do not come into contact with brass or copper. However, if it is unavoidable, then extra measures should be taken to ensure that electrical contact between the two surfaces does not occur, and water should not flow from the brass or copper surfaces onto the galvanized steel posts.