Can You Weld Zinc Plated Steel? What You Need to Know!
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Zinc plated steel refers to steel covered with a layer of zinc through electro-galvanization. The zinc layer prevents rusting and corrosion. Now, a common concern is whether zinc-plated steel can be welded, considering the melting properties associated with the zinc coat. Yes, you can weld zinc plated steel with other alloys, provided you follow the correct procedure to create robust, clean, and durable welds that do not break or crack easily.
However, you must understand that zinc-plated steel contains materials with different properties, and you will need to know how they react when exposed to varying degrees of temperatures during the welding process. Also, note that welding zinc plated steel is dangerous and expensive, so you need to take precautionary measures against dangerous fumes produced during the welding process.
Read on to find out why steel is coated with zinc, the hazards posed by welding zinc-coated steel and the solutions, the different methodologies, and the steps involved in welding zinc-plated steel.
Why Is Steel Coated with a Zinc Layer?
As much as steel is a strong metal, it’s still vulnerable to oxidation, which is caused by the exposure of the surface to air and moisture. Moisture will lead to rusting and the wear and tear of steel, consequently weakening it.
Coating it with zinc offers better protection against weathering elements, thus shielding the metal from rust, moisture, and oxidation, and improving its stability. When exposed to oxidizing agents, zinc corrodes at approximately 1/30 the rate of natural and untreated steel. This makes zinc plated steel highly resistant to rust and corrosion.
Difference Between Zinc Plated Steel and Galvanized Steel
Sometimes people do not understand the difference between galvanized steel and zinc plated steel. This is because both metals feature a steel plate covered with a layer of zinc to protect against oxidation. Galvanized steel, however, has a thicker zinc surface compared to zinc plated steel.
The method used to make zinc plated steel is also similar to galvanized steel plate but with one major difference. Zinc plated steel plates are made using an electric current, while galvanized steel is created using the hot-dip method.
The hot-dip technique involves smelting zinc particles in a furnace and submerging steel in the molten zinc. This creates a solid barrier that protects the steel from rusting caused by oxidation.
Dangers Involved with Welding Zinc Coated Steel
Zinc and steel are different in many ways. This ranges from physical properties, behavior, and chemical composition.
When exposed to heat, steel has a higher boiling point than zinc. It melts at a temperature of 1,400°C, while zinc melts at a temperature of 420°C and boils at 709°C. This means that while welding, the zinc coating will not only melt but vaporize by the time the steel plate is hot enough to weld it.
In addition, you don’t benefit from the zinc coating in the areas welded because vaporized zinc tends to get trapped on the surface of the steel, creating bubbles inside the weld. These bubbles can weaken the weld making it fragile and susceptible to breakage and cracking.
Another notable risk is that when exposed to the high temperatures of a welding process, the reaction of the chemical compositions of both zinc and steel can cause adverse effects on the welder’s health.
This is where the dangers of welding zinc plated steel sheets lie in. When the weld pool starts melting, zinc releases a hazardous toxic fume. A welder risks breathing in the vaporized zinc, which can create respiratory issues.
One common respiratory issue is metal fume fever. It is an industrial disease caused by inhaling zinc-coated particles. The symptoms of this disease are normally similar to common flu and other lung-related discomforts. The flu-like symptoms may last for a couple of days but prolonged exposure to these fumes can cause irreversible lung damage or increase your susceptibility to other diseases, including cancer.
Safety Measures and Solutions
The best way to minimize the hazards posed by welding zinc plated steel is to weld the different metal alloys before zinc plating. Well, this may not always be possible because it’s hard to weld the material before coating them with zinc, while you could simply purchase zinc plated sheets from your local hardware.
If you happen to be welding with a zinc plated steel sheet, you can remove the whole zinc coating layer using a hydraulic acid pickle. If this option is not available, you can carefully weld the zinc plated steel sheets while ensuring the surrounding areas don’t get too hot.
- Always have a respiratory mask on before welding.
- Your workspace should be well ventilated and workers sensitized to the dangers of zinc vapor. Welders working in confined areas such as deep open tanks should have sufficient air supply directed into the tank via a fan or blower. Use local exhaust ventilation if you cannot evade the zinc fumes produced by welding zinc plated steel.
- Use low-temperature welding tools and equipment that will not get too hot and vaporize the zinc layer from the steel surface. These include TIG welders, oxy-acetylene, and zinc filler rods.
- Try to manually scrape off the zinc coating from the welding area before embarking on the wedding process.
How to Weld Zinc Plated Steel
There are different methods that you can use to weld zinc plated steel. But first, here is how to remove the zinc coating:
In this method, a welder has to scrap the zinc surface manually before beginning to weld. This way, you get to remove the zinc, which evaporates from the high temperatures emitted by a welder. It is, however, a dangerous method, so you need to protect your body using the latest safety equipment, including welding gloves, jacket, and helmet.
In this method, you must be prepared to heat the weld to high temperatures to ensure the zinc plates naturally vaporize off the steel surface. Make sure to cover your face to prevent the inhalation of the zinc vapor. This method is best suited for workspaces with sufficient ventilation.
Once the zinc coat is off, you can proceed to weld the naked steel using the methodologies below:
Carbon Arc Welding
This is one of the most popular zinc plate welding methods because it utilizes twin carbon touch as the heat source. You can direct the arc to the filler rod to produce enough heat to weld the zinc plated sheets but not too hot to destroy the zinc coating. Carbon arc welding is advantageous because it reduces the need for refilling, replating, and re-galvanizing.
Gas Tungsten Arc Welding
The GTAW method of welding zinc plated steel is a slower method that tends to destroy and deplete zinc particles on the welded steel. This technique also makes the electrode susceptible to contamination by volatilized zinc, which requires constant redressing. When the temperatures are high, the more likely the zinc plating will be destroyed because of its lower boiling and melting temperatures.
Steps to Follow When Welding Zinc Plated Steel
1. Put on Safety Gear
Due to the safety hazards posed by the welding fumes, it is crucial to have safety gear capable of protecting you from heat, sparks, and toxic fumes. The safety equipment that is best suited to handle these hazardous fumes includes an apron, a helmet, a respirator, and welding gloves.
Whenever you can, weld your metals in an open area to reduce the chances of inhaling the fumes. If working indoors, ensure the windows are always open to release the toxic fume out of your workplace. A fume extractor or regular fans can also assist in ventilating your workplace.
2. Clean the Surface
Before you start the welding process, clean the surface of the zinc plated steel using a grinder or sandpaper. This helps clear off any debris created by the vaporizing zinc or any oxidation that occurs on the base metal surface.
3. Clamp the Pieces
Adjust the zinc-coated plates accordingly to avoid creating unstable welds. Welding clamps are the best for small chunks of metal and also help welders get the required seam.
4. Select Welding Rod
The welding rod should be able to handle the different sizes of metal you will be welding. It should also work smoothly with your welder.
5. Start Welding
When you have ridden off the zinc, begin the welding process. The process is very standard, and you can even use a standard welder to weld the zinc-less steel base. This method is also very versatile, allowing users to use both TIG and MIG welding. You just need to be very careful when grinding the zinc plate.
So, can you weld zinc plated steel? If the metal alloy to be fused is made from the same parent stock, then the answer is yes. However, you have to take precautionary measures to mitigate the potential danger and health hazards involved with welding zinc plated steel.
To make the best out of zinc plated steel welding, ensure that you weld in a sufficiently ventilated workspace. Alternatively, use a welding method that is hot enough to fuse the metals, but not too hot to vaporize the zinc coating from the surface of the steel.
Featured Image Credit: khathar ranglak, Shutterstock