To help you better understand Daam Galvanizing and galvanizing in general, we have provided answers to some frequently asked questions. Should you have any additional questions, please don’t hesitate to contact us.
How does galvanizing protect steel from corrosion?
Zinc metal used in the galvanizing process provides an impenetrable barrier between the fabricated steel and corrosive elements in the environment. More importantly, galvanizing protects steel by providing cathodic protection. The zinc corrodes first, thereby protecting the base steel.
What are the steps in the galvanizing process?
- Step 1: Pre-inspection: The fabricated structural steel is viewed to ensure it has the proper venting, draining holes and overall design characteristics necessary for galvanization.
- Step 2: Cleaning: Steel is immersed in a caustic solution to remove grease and dirt. It’s then dipped in a hydrochloric acid bath to remove mill scale and rust. Finally, it’s lowered into a bath of flux that promotes a reaction between the zinc and steel. Steel will not react with zinc unless it’s perfectly clean.
- Step 3: Galvanizing: The bath of molten zinc and the clean steel metallurgically react to form three, zinc-iron intermetallic layers and one, pure zinc layer.
- Step 4: Final inspection: The newly galvanized steel is sight-inspected and hand filed to the end use requirements.
How does the cost of hot-dip galvanizing compare to paint systems?
Hot-dip galvanizing has lower initial costs and almost always lowers the life-cycle cost of a project. In comparison, paint requires maintenance, partial repainting and full repainting over a product’s life cycle. If you would like to perform a cost comparison between hot-dip galvanizing and a specific painting system, please contact us.
How long will galvanized steel last?
Hot-dip galvanized steel resists corrosion in numerous environments and can last as long as 150 years under certain conditions. The corrosion rate of the zinc is directly related to the function of the coating thickness and the amount of corrosive elements in the environment.
How does the coating resist abrasion?
Three, intermetallic layers are formed that are harder than the fabricated steel for excellent resistance against abrasion.
Can galvanized steel withstand high temperatures?
Constant exposure to temperatures below 200C is an acceptable environment for hot-dip galvanized steel. If exposed to temperatures above 200C, good performance can be achieved if exposed on a periodic basis.
What are the size limitations? If an item is larger than your kettle dimensions, can it still be galvanized?
Our Edmonton tank size is 12.6m long by 1.07m wide and 2.44m deep. Our Saskatoon tank size is 6.55m long by 1.092m wide and 1.37m deep. If required, a progressive dip, commonly referred to as a “double dip”, can be performed. This occurs when we dip one half of the steel in the molten zinc, remove it and dip the other half. If it’s possible to splice the product to fit in the tank, then it’s more cost effective to hot-dip galvanize. Click here to see our “double dip” chart for our Edmonton plant, and click here for our “double dip” chart for our Saskatoon plant.
What design and fabrication considerations do I need to make prior to hot-dip galvanizing my steel?
Fabricated steel must allow for easy flow of the cleaning chemicals and allow molten zinc metal to run over and through it. Click here to see our design details sheets.
What type of products can be galvanized?
Most ferrous materials are suitable and can be protected from corrosion with hot-dip galvanizing, including:
- Cast iron
- Malleable iron
- Cast steels
- Hot rolled steel
- Cold rolled steel
Structural steel shapes, including those of high-strength and low-alloy materials are hot-dip galvanized after fabrication to obtain long lasting protection. Please contact us to ensure your material is suitable for hot-dip galvanizing.
Why is my steel shiny in one area and matte in another?
The outer layer of pure zinc creates the shiny appearance on steel. If the steel has a matte finish, the coating’s intermetallic layers are exposed. The appearance depends on the amount of zinc in the metallic layers and the thickness, roughness, chemistry (such as the amount of silicon and phosphorus) and design of the steel being galvanized. Performance is never affected.
What causes distortion warpage and can we determine what pieces may be affected prior to galvanizing?
Minimizing warpage and distortion is preferably done in the project’s design stages. This can be done by selecting equal thicknesses of steel for each individual piece being dipped, using symmetrical designs and avoiding the use of light-gage steel (<1/16”). Some structures may require temporary bracing to help maintain their shape.
Can I paint over galvanized steel?
Painting galvanized steel, whether required for aesthetics or extending the life of the structure, can be done. Please refer to ASTM D 6386, Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting, for suggested surface preparation methods for galvanized steel.
How much weight will my material gain from galvanizing?
As an average, the weight will increase by around 5–6%. That figure can vary based on shape, size and steel chemistry.
Why do we need to design for venting and drainage holes?
The cleaning solutions and molten zinc metal need to flow entirely through and over a product to ensure proper corrosion protection. Without vent holes, air and gases will get trapped in the product and an area of black steel will be exposed to the elements, resulting in corrosion over time. Click here to see our design details sheets.
Can I use stitch-welding?
Yes. Click here to see our design details sheets.
My hot-dip galvanized steel is white. What is this and how can it be avoided?
A wet storage stain, sometimes mistakenly referred to as “white rust”, is a result of the galvanized steel being stored in a wet or humid environment for an extended period of time. The largest contributor to this problem is improper site storage that creates pockets of moisture on the product. Daam Galvanizing recommends that all hot-dip galvanized materials are stored to allow for proper drainage, reducing the chances of wet storage stains. Once the steel is in service, wet storage stains typically weather away.
Can I partially galvanize certain areas of my steel assembly?
Silicon masking can be done prior to the galvanizing process, but it’s only 50% effective and leaves residue on the steel. Another option is to apply gorilla tape on the required area. This is more effective than silicon masking, but still not 100% effective. We do, however, partially dip structural piles if required.