Galvanized coatings on steel are intended to last for decades without requiring maintenance. But if you’re welding galvanized steel, you need to remove the zinc coating, or you’ll risk premature corrosion of your weld joint. The zinc coating can create an electrical current that interferes with the welding process.
To get a good weld, the galvanized coating must be removed. But how to remove galvanized coating for welding to avoid many problems? There are many methods you can use to remove the galvanized coating.
Removing galvanized coating is an easy process, but it’s important to do it correctly. We will discuss some easy steps for removing galvanized coating for welding purposes throughout this article.
How to Remove Galvanized Coating for Welding – Easy Methods
Galvanized metal is steel that has been coated with a layer of zinc coating to protect it from corrosion. This coating can make it difficult to weld galvanized metal, as the zinc prevents the arc from forming correctly.
However, there are a few easy ways to remove the galvanizing before welding.
Method 01. Using an Angle Grinder With a Flap Disc:
Using an angle grinder with a flap disc is the quickest and most effective way to remove the galvanized coating from steel. This method will also remove any rust present on the steel.
Start by donning personal protective equipment, including gloves, eye protection, and a dust mask. Then, position the steel so that the area you wish to remove the galvanizing from is facing up. Next, attach a 40-grit flap disc to your angle grinder. Be sure to wear ear protection as well.
Begin grinding at a low speed and increase the speed as you go. Apply moderate pressure to the flap disc as you work your way across the surface of the steel. After a few minutes, you should see the galvanized coating flake off.
Continue until all of the coatings have been removed. Finally, wipe down the steel with a clean cloth to remove residual dust particles. However, if your galvanization is thick, a grinding disc may be more appropriate. This is due to zinc’s tendency to congest flap discs.
Method 02. Try to Use Flame Cleaning:
Flame cleaning is often the most effective formula for removing galvanized coating for welding. You will need a propane torch and some wire brush attachments for this method. It is recommended that you wear gloves, safety goggles, and a respirator when performing this method.
The process is fairly simple, a propane welder’s torch is passed over the surface of the metal, carefully heating the zinc until it vaporizes. This method is often used on larger projects where a power washer or chemical stripper would be impractical.
It’s essential to be cautious when using this method, as it’s easy to overheat the metal and cause damage. However, flame cleaning is an effective way to remove the galvanized coating from steel when done correctly.
Using this technique, thick galvanization can be removed without causing damage to the metal, leaving a smooth surface that does not contain any residual zinc.
Method 03. Using a Hammer and a Chisel:
Using a hammer and a chisel to remove the galvanized coating is a quick and easy method that anyone can do:
- First, use the chisel to score the coating around the weld area that you want to weld.
- Next, use the hammer to tap along the scored line. This will loosen the coating and make it easier to remove.
- Finally, use the chisel to pry the coating off of the metal. Repeat this process until all of the galvanized coatings have been removed from the area that you need to weld.
This method is best for small areas or for removing only a very thick layer of coating. If you are working with a large area or need to remove a thick layer of coating, you may need to use a different method.
Method 04. Abrasive Blasting (Sandblasting):
Abrasive blasting is a popular method for removing galvanizing coating from welds. Using high-speed abrasive particles, abrasive blasting materials are the aggressive process that removes thick galvanized layers at high speeds. This method is also helpful for cleaning hard-to-reach areas.
Sandblasting is one of the most widely used abrasive blasting materials involving sand and a powerful air compressor. This process involves using high-pressure air to blast abrasive blasting sand at the surface of the welding joint.
Abrasive blasting is an effective way to remove the galvanized coating, but it can also damage the base metal and surrounding areas if not done correctly. Abrasive blasting or sandblasting should only be done by experienced professionals familiar with the risks and dangers involved.
Method 05: Muriatic Acid Method:
Acid Muriatic is a powerful acid that can be used to remove the galvanized coating from steel. This method is best suited for small projects where only a few inches of galvanized coating need to be removed.
It can be found at most hardware stores and is relatively inexpensive. When using this method, it is essential to protect your skin and eyes from the acid. Muriatic acid will also remove any paint or other coatings on the steel, so it is important to use this method with caution:
- First, the area to be etched should be cleaned with soap and water.
- Next, the muriatic acid should be diluted with water according to the manufacturer’s instructions. The diluted acid should then be applied to the galvanized coating with a brush or sponge.
- After a few minutes, the acids will eat away at the galvanized coating. The longer the acid is allowed to work, the more of the coating will be removed.
- Once the desired amount of coating has been removed, the area should be rinsed thoroughly with water to neutralize the acid.
- Finally, the bare steel should be primed and painted to protect it from rust. This method can be time-consuming and dangerous, but it effectively removes the galvanized coating from steel.
The Consequences of Welding Over Galvanized Surfaces
Galvanized surfaces are coated with a thin layer of zinc, which helps to protect the metal beneath from rust and corrosion. However, when welding over galvanized surfaces, the heat of the arc can cause the zinc to vaporize.
Inhaling these fumes can be dangerous, and can lead to a condition known as metal fume fever. Also, there are some problems that can occur when welding over galvanized surfaces:
01. Heat-Affected Zone (HAZ):
Welding over galvanized surfaces can have several consequences, the most significant of which is the Heat-Affected Zone (HAZ). The HAZ is the area around the weld that has been heated to such a high temperature that it has changed the properties of the metal.
The HAZ can be significantly larger than usual when welding over galvanized surfaces, weakening the overall structure. In addition, welding over galvanized surfaces can produce toxic fumes, harming both the welder and any nearby bystanders.
02. Excessive Spatter and Smoke:
Excessive spatter and smoke can be a major problem when welding over galvanized surfaces. The high temperatures of the welding arc cause the zinc in the galvanized coating to vaporize. This zinc vapor condenses on the weld pool, resulting in spatter and smoke.
In addition, zinc vapor can also react with the oxygen in the air to form zinc oxide, which is a highly corrosive material. If too much zinc oxide is produced, it can cause the weld pool to become unstable and lead to welding defects. As a result, it is imperative to avoid excessive spatter and smoke when welding over galvanized surfaces.
03. Excessive Porosity:
Excessive porosity is one of the main dangers of welding over galvanized surfaces. The zinc in the galvanized coating reacts with the iron in the weld to create a zinc-iron alloy. This alloy is highly porous and can cause major problems with the strength and stability of the weld.
In addition, porosity can trap moisture and other contaminants, which can lead to corrosion. As a result, it is important to be very careful when welding over galvanized surfaces to avoid excessive porosity.
04. Low Root Penetration:
Welding over galvanized surfaces may result in low root penetration. When welds are made on galvanized steel, the zinc coating is vaporized and can condense on the roots of nearby plants. This can cause the roots to become chlorinated and die.
Moreover, zinc can also inhibit the roots’ uptake of water and nutrients, leading to stunted growth or even death. As a result, it is vital to take precautions when welding on galvanized surfaces, such as ensuring that the area is well-ventilated and using a respirator to avoid inhaling zinc fumes.
05. Harder Arc Strikes:
Welding over galvanized surfaces can have several consequences, one of which is harder arc strikes. Harder arc strikes are necessary when removing the galvanized coating from a steel surface. This is because the zinc in the galvanized coating can interfere with the formation of the weld pool, making it more difficult to form a strong bond.
Additionally, welding over galvanized surfaces can release harmful fumes that can be dangerous to breathe in. As a result, it is important to take precautions when welding over galvanized surfaces and ensure that the area is well-ventilated.
Removal of Galvanized Coating: Precautions
Most people are familiar with the galvanized coating often used to protect metal surfaces from corrosion. However, there may come a time when you need to remove this coating:
01: Try to Work Outside:
When working with galvanized steel, it’s important to take precautions against exposing yourself to the fumes generated by removing the galvanized coating. Try to work outside if possible, and if you must work indoors, make sure the area is well-ventilated.
Wear a dust mask and gloves, and avoid touching your face or eyes while working. In addition, it’s essential to dispose of any waste material properly to prevent contamination of the soil or water supply.
02. Leave Windows and Doors Open:
It is important to take all the necessary precautions when working with chemicals of any type. This is especially true when removing the galvanized coating from steel. Chemical fumes can be hazardous, so it is important to work in a well-ventilated area. Leave all windows and doors open to get as much air circulating as possible.
In addition, wear gloves and a face mask to protect your skin and lungs from the fumes. If you experience any dizziness or nausea, stop working immediately and move to an area with fresh air.
03. Stay Away from the Pollutants’ Path:
Always stay away from the path of any potential pollutants. This means staying upwind and up-current from any area where the galvanized coating is being removed. In addition, you should wear a respirator or some other type of protective gear to avoid inhaling any fumes or particulates that may be released into the air.
04. Use a Quality Respiratory Mask With P100 Filters:
When removing the galvanized coating from metal, it is important to take precautions to protect your lungs from the fumes. The best way to do this is to use a quality respiratory mask with P100 filters. P100 filters are designed to filter out 99.97% of airborne particles, including those that are too small to be seen with the naked eye.
This will help to ensure that you breathe in only clean air and avoid inhaling any harmful fumes. In addition, it is also important to work in a well-ventilated area to help reduce the risk of exposure.
By taking these precautions, you can help to keep yourself safe when removing the galvanized coating from metal.
FAQs
Here are some frequently asked questions about removing the galvanized coating from metal:
01. Can You Remove the Galvanized Coating?
Yes, you can remove the galvanized coating from the metal. If you’re only removing a light layer of galvanized coating, you can often just use a simple household cleaner like acetic acid vinegar or lemon juice.
02. Can You Grind Off Galvanized Coating?
Galvanized coatings can be ground off using a variety of methods. The most common method is to use a power grinder with a grinding disc designed for galvanized metal. Another method is to use a hand-held power drill with a wire brush attachment. You can also use a hand-held power sander with sandpaper designed for galvanizing.
03. Is it Safe to Grind Galvanized Metal?
Yes, it is safe to grind galvanized metal. Galvanized metal is coated with zinc coating, protecting the metal from corrosion. The zinc is abraded away when grinding galvanized metal, revealing the unprotected metal beneath.
04. Why is Galvanized Steel Poisonous?
Galvanized steel is poisonous because it releases zinc fumes when the zinc coating corrodes. Zinc fumes are hazardous because they contain a high level of zinc oxide, which can cause lung damage and even death. For this reason, galvanized steel should never be used in construction or anywhere else; people might be exposed to fumes.
05. Can You Burn Galvanized Metal?
When welding galvanized metal, it is important to use the correct type of electrode and welding rod. Otherwise, you run the risk of creating hazardous fumes. Inhaling welding fume in these circumstances can cause Galvanite Poisoning, which can be fatal. For this reason, it is not recommended to burn galvanized metal. So, keep in mind to keep the temperature below 392 F (200 C), otherwise, you are at risk of a fire hazard.
06. Can You Sand off Galvanized Coating?
Yes, You can Sandblast Galvanised Coating. Abrasive blasting is a popular method for removing galvanized coatings, as it is effective and does not require the use of chemicals. But, you run into the risk of harming the underlying metal.
If you want to remove the galvanized coating without damaging the underlying metal, you can use a chemical stripper. Chemical strippers are designed to dissolve the zinc without harming the metal underneath
Conclusion
When welding galvanized steel, it is essential to remove the galvanized coating first. Otherwise, the zinc will vaporize and create hazardous fumes. With the coating removed, you will be able to weld galvanized steel safely and effectively.
learning how to remove galvanized coating for welding is essential for every welder. Removing galvanization coating from metal can be a difficult task, but it’s definitely doable. With the right tools and methods described in this article, you can have that galvanized coating off in no time. And once it’s gone, you’ll be one step closer to starting your welding project.