Before welding any metal that you’re a stranger to, you should always do lots of research to ensure that you’re not putting yourself or your workers at risk. Zinc-fumes can be extremely dangerous if inhaled, but as home and car designers alike are requesting more zinc in their services – the welder who can work with zinc becomes an important figure on the market.
How to Weld Zinc
Zinc has a relatively low boiling point for a metal, and this can cause trouble for welders. If your welding temperature is too high, you could vaporise the zinc – causing a release of dangerous and toxic gas that produces severe, flu-like symptoms when inhaled. This makes it extremely important to wear a respirator if you’re going to weld zinc, ensure the workshop is extremely well ventilated and that all workers are aware of the dangers and how to handle and minimise risks.
Once you’re aware of the dangers of zinc and its poisonous fumes, you’ll need a TIG machine, zinc filler rods and oxy-acetylene fuel. After this, welders online claim that the process is very similar to welding aluminium. Oxy-acetylene is recommended because it works at lower temperatures than other popular welding gases, and zinc requires lower temperatures than the metals that welders are typically used to.
Steel is a metal with a lot of very useful qualities, so it is also one of the most frequently welded metals, alongside aluminium. By coating steel with zinc, however, you add properties to the steel that enhance it further – such as higher resistance to corrosion – but when it comes to welding this strange fusion of metals, some welders can be left scratching their heads.
Understanding how to weld zinc-coated steel can be very important too, as the need for this fusion in modern appliances increases. For example, if you read our Car Chassis Welding Tips guide, this section will be important for you because there is an increasing conversion of automotive chassis components to galvanised steels (zinc-coated steels).
The Lincoln Electric Company have reported that the GMAW process typically used for welding chassis components has had inconsistent results for coated steels. To understand how to weld zinc, you need to understand how and why it behaves in particular ways in welding situations.
Zinc has a relatively low boiling temperature compared to steel, but to weld a coated steel your welding torch will need to meet the required higher temperature for steel welding. The effect of this in practice is that when welders start work on these materials, the zinc is vaporized and becomes trapped in the steels.
This vaporised steel creates bubbles along and inside the weld, known as porosity, and this compromises the strength of the weld – making it more brittle and fragile.
The vaporised zinc also causes disturbances to the welding environment, increasing the likelihood of spatter and disrupting the arc – and therefore, the flow of the welding bead. This can further affect the structural integrity of the weld.
If you’re struggling with any of the terminologies in this guide, we recommend that you take a quick look at our Welding Terminology
This means that you should be looking towards common welding techniques for reducing porosity, such as reducing the welding speed. This is a good solution if you’re a hobby welder, but in a business where every minute counts towards profit – you might not be too keen on advising your workers to lower their weld speeds for galvanised steels.
If you’re worried about the dangers of vaporising the zinc coating, you could also grind the zinc away in the area surrounding the welding zone. This means that the coating will need to be reapplied afterwards if those anti-corrosion qualities are important for the end product.
If you are planning to grind off the coating and re-dip the part, you will need to be especially wary of spatter and plan methods for cleaning this off before the coating is reapplied. Spatter and slag can disrupt the coating, and if there’s a flaw in the coat corrosion could sneak in and spread below the surface.
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