Welding galvanized steel needs prepping first for it to weld like undercoat carbon steel. Attempting to weld galvanized steel without first removing the galvanizing coat results in formation of weld pop, or blow out which creates a health hazard. Can you weld galvanized steel? This depends on your preparation.
How to Prep Galvanized Steel for a Weld?
Removing the galvanizing from your galvanized steel is a priority. You can do this using a flapper wheel, hard wheel, or a grinding disc attached to your grinder. First, hold the grinder at an angle of 15-degrees to your galvanized metal then make long passes along your weld area. Apply light pressure to your grinder. The 15-degrees angle ensures that only a small amount of carbon steel is removed during this grinding process besides the zinc coating.
Alternatively, you can use a coarse grinding disc or wheel but you will have to make more passes using a finer grit grinding disc or flapper wheel to remove all the galvanizing.
Can Welding Galvanized Steel Make You Sick?
If you don’t remove the galvanizing, you run the risk of galvanize poisoning which will make you sick. Welding without removing the galvanizing coat emits noxious yellow-green heavy smoke which results in galvanize poisoning if the exposure is continuous.
Symptoms of galvanize poisoning include severe nausea and headache. You can reduce these symptoms by getting fresh air or drinking more milk and taking calcium supplements to curb stomach upsets. Overexposure to galvanize poisoning can result in death.
Nowadays, there are ventilation welding hoods that are useful in reducing the smoke amount you inhale when welding. Alternatively, you can use a respirator to avoid inhaling toxic zinc oxide fumes or weld in a properly ventilated environment.
How to Weld Galvanized Steel
After removing the galvanizing, you can weld steel to galvanized steel. The welding process is similar to that of uncoated carbon steel. You can use all standard welding forms and prepping practices. You can use flux core wires, but you need a high degree of skill and patience. Do the welding in a well-ventilated area and wear protective gear for safety.
Welding galvanized steel is hard and you need serious prepping otherwise the zinc oxide coat will contaminate your weld or cause porosity and inclusions. Also common is the lack of fusion at the ends of the welds. To avoid these risks, use proper welding techniques and remove the zinc coating before welding. Use a filler metal made for zinc-coated metals.
Welding galvanized steel burns away the zinc coating leaving the surface uncoated and unprotected. To maintain corrosion resistance after welding, paint the surface or re-galvanize. Unprotected bare weld is prone to expedient weld failure.
Welding Galvanized Steel Using a MIG Welder
A standard MIG welder uses inert gas to maintain uncontaminated weld. MIG is commonly used because it produces cleaner welds thanks to the shielding gas. However, a standard MIG process is not preferred when welding galvanized steel.
Step 1: Remove the MIG Wire
We don’t use standard MIG wire because it doesn’t have enough scavengers to effectively weld galvanized steel. Therefore, change the wire in the MIG welder to flux core. Rewind the standard wire to remove it then fasten the end to your spool.
Step 2: Replace the Drive Roll and Insert Flux Cored
The flux core is hollow, meaning it needs a drive roll with serrated teeth to move the flux wire through your MIG gun without causing damage. Replace the drive roll by first removing the small bolt then replacing it with the serrated roll. Carefully attach the flux cored spool then feed the cord carefully into the MIG welding gun through the machine.
Step 3: Change the Polarity
In flux-core welding, we use negative (DC) polarity. To switch polarity, change the wire in the MIG welding machine connected from the MIG gun to the negative from the positive.
Step 4: Grind off the Galvanizing Coat
Wear protective gear and your respirator before you start grinding the zinc-oxide coating. Use a grinder or sander to remove the zinc coating then wipe the surface dry using a dry towel.
Step 5: Weld the Bare Metal
MIG welding mostly requires welders to push their welding pool forward. However, when welding galvanized metal, pull rather than pushing the weld. The flux will keep your weld pool free of contaminants, which may not happen effectively if you are pushing the weld forward. Pushing the weld results in porosity and you get a weak weld.
Step 6: Re-galvanize your Metal
After cleaning the spatter and slag, use your galvanizing spray to re-coat the bare metal to protect it from corrosion.
How to Weld Galvanized Steel Pipe Using an Arc Welder?
Welding galvanized metals is unlike raw steel because galvanized metal pieces are difficult to weld. A welder must take some precautions because of the toxic fumes released during the welding process.
Step 1: Organize your Work Area
The welding process should best be done outdoors because of the toxic fumes. Also, you can do it in a well-ventilated area preferably a big room with windows. Install a fume extractor or fans that can blow away the fumes. Be ready with a wire brush for cleaning the welds when done.
Step 2: Wear Protective Gear
Have a high-quality respirator when dealing with galvanized steel. Also, get a premium welding mask, apron, and gloves for protection against spatter.
Step 3: Grind the Zinc Coat Off
Use a power sander with 220-grit sandpaper if you are dealing with a large galvanized steel piece. For pipes, simply use a grinder.
Before you start, wear your protective gear to avoid inhaling zinc fumes. Grind the zinc-coated area you want to weld thoroughly and remove 2-inches of coating below and above the weld area. When finished, wipe the surface using a dry cloth.
Step 4: Weld the Bare Steel
Pull the welding arc slowly against your welding section. For long welds stop and clean off the weld spatter periodically.
Alternatively, you can use an anti-spatter gel. When finished, use your wire brush to clean the weld and remove the slag.
If you see any signs of bubbling close to the weld, then you have porosity meaning you failed to remove sufficient zinc coating when grinding. You must strip the whole zinc coating for you to get a sturdy and clean weld.
Step 5: Galvanize the Weld Area
The bare metal is prone to corrosion because the zinc coating is gone. Re-apply the zinc coating to your bare steel to protect it against corrosion. Remember to use a respirator and eye protection when reapplying the zinc coat spray.
Can I Weld Steel with a Propane Torch?
This is not advisable because a propane torch doesn’t achieve the high temperature necessary to weld steel. The propane torch is hot enough to braze but not enough to weld steel.
Also, the weld pool oxidizes quickly during the welding process. However, propane torch is ideal for silver solder, heating, cutting, and brazing.
Oxy-propane can achieve a high temperature of 1800 degrees Celsius.
Is Heating Galvanized Steel Bad?
Heating galvanized steel releases zinc fumes which causes galvanizing poisoning or metal-fume fever. The galvanized coat performs better in extremely cold temperatures. Weld galvanized metals in well-ventilated areas to minimize health risks. Heating galvanized steel shouldn’t go beyond 200 degree Celsius as toxicity risk increases from there.
What Is the Best Welding Rod for Galvanized Steel?
E7018 is the best welding rod to use on galvanized steel. The rod is versatile and coated with iron powder and a low hydrogen potassium mixture. The welding rod is compatible with DC+, AC. DC- currents. Besides, it’s the most effective welding rod for hard to weld metals like galvanized steel and produces more uniform welds. The welds can withstand harsh conditions like subzero temperatures and extreme temperature fluctuations.
The E7018 weld rod forms crack-resistant welds in alloy steels, medium, and high carbon steels requiring minimum tensile strength of at least 70,000 psi. The welder enjoys a high deposition rate and the slag formed at the weld bead is easily removed although heavy. The strong weld beads and versatile electrodes are the reason the E7018 welding rod is used to weld offshore drill rigs and sections of power plants.
Conclusion
Welding galvanized metals is challenging because of the zinc coating which complicates your welding process. Always work in a well-ventilated room or weld outside. Regardless, of whether you choose a MIG welding machine or welding arc, never forget to wear your protective gear. Observe all safety precautions and have your calcium supplements, and milk close in case you inhale the toxic metal fumes.
