Hot dip galvanization 3 Steps -The art behind anti-corrosive iron and steel

Certain things are ageless because they cannot be improved, aren’t they? Let us add something interesting to this list that most people don’t think about — hot-dip galvanization. Did you know that this process has its roots dating back to 1742? Despite advances in technology in every field, hot-dip galvanization continues to stand miles ahead of competitive processes with various benefits like cheap cost, durability, longevity and corrosion-resistance. It has successfully held its ground for over 4 centuries. 

What is Hot-dip Galvanization ?

Look around closely and you will find hot-dip galvanized steel and iron everywhere. The metals dominate in a variety of industries — road, railways, energy plants, oil and gas plants, agriculture, water, waste, sports and leisure, etc. Whenever there is threat of corrosion to surfaces and structures, hot-dip galvanization emerges as a hero. Galvanized steel and iron are most commonly found in buildings, bridges, gates, etc.  where corrosion can be very dangerous, and not just ugly. The process of hot-dip galvanization involves dipping metals in molten zinc at high temperatures which facilitates multi-layered coating of zinc-iron alloy and zinc metal on the surface, which is corrosion-resistant. The temperatures during the process range between 438 to 460°C.

How is it done?

Hot-dip galvanizing doesn’t just start and end at dipping iron or steel in the molten zinc solution. There is pre and post-treatment required at the manufacturing plant that make the substance failsafe. The process involves the following steps:

1.Surface preparation

Before dipping, the surface should be completely clean and free from impurities like grease, dirt, mill scale, etc. because galvanization will fail if the metal is unclean. Surface preparation is an absolute necessity which involves three main processes:

Degreasing: The surface of the metal contains impurities like dirt, grease, etc. It is purged by an alkaline caustic solution that gets rid of the organic contaminants followed by rinsing with water.

Pickling: The next step involves removal of oxides and mill scale by pickling in a dilute solution of hydrochloric or Sulfuric acid after which rinsing in water is repeated.

Fluxing: To prevent further oxidation of the surface after pickling, a protective coating is needed. This is when the surface is dipped in zinc chloride and aluminum chloride solution. In some galvanizing plants, flux floats over liquid zinc in the galvanizing kettle itself.

2.Hot-dip Galvanization 

This is the main process wherein molten zinc solution waits for iron or steel to be lowered at an angle in the hot-dip galvanizing kettle. The   metal remains dipped till it heats up to bathing temperature to allow the diffusion reaction of iron and zinc.

Post treatment
Post treatment might be necessary if the galvanized steel or iron is made for places with rough conditions. This process protects steel or iron from damage during transportation and storage.

 How long does it take?

The galvanization process alone takes not more than 10 minutes. However, depending on the shape of the metal being galvanized, the duration might go up or down. The entire process from start to end can be wrapped up within 3 days usually.

Advantages of galvanizing

There are multiple benefits of galvanized steel and iron that has made it the process of choice for centuries:

  1. Low cost — Compared to most other methods for protecting steel and iron, this method is the cheapest.
  2. Longevity — The shelf life is at least 50 years. Thus, there’s not much to worry about once the process is completed.
  3. Maintenance — Due to the thick coating, frequent maintenance is not needed. Who doesn’t want to save time, money and effort?

 Hot-dip galvanized steel and iron are hence highly recommended. They possess not just the muscle but also the age to last without any   external interference. Further, their inspection can be concluded by the looks of it — if there are no visible blemishes, it signifies that it is     actually in a perfect shape. While the galvanizing processes are getting upgraded with technological advancements, the basics remain the   same. There is reason to believe that the legacy of hot-dip galvanization that started in the mid-eighteenth century will continue the     marathon for more centuries. For more information Contact us at pinaxsteel.com