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What is The Best Flux for Soldering Sheet Metal?

What is The Best Flux for Soldering Sheet Metal?

When you are soldering any type of sheet metal, it is very important to choose the right flux.  Flux is made of an activator and a carrier that allows the solder to “wet” to the base metal surfaces.  The flux removes the oxides from the metal to prep the surfaces for bonding with the solder.

Further, by having the correct flux, it can make the connection much smoother, and you will get a much better performance out of soldering.

The best flux for soldering most sheet metal variations should be a strong and active flux with effective ingredients that are necessary for soldering.

Below are some recommendations for the optimal flux for different types of sheet metal:

Recommended Flux for Sheet Metal Soldering:

1. Best Flux For Stainless Steel Soldering

For soldering stainless steel, the best choice of flux is an aggressive flux.  No-clean fluxes and rosin flux won’t work well for soldering stainless steel. The best flux for stainless steel is a high-activity flux that has a phosphoric acid base.  A high activity flux can help make the soldering smoother because stainless steel has tenacious oxides on its surface.  These oxides can stop the soldering from sticking to the steel surface.

2. Best Flux For Soldering Galvanized Steel Sheet Metal

For soldering galvanized steel, the right flux will get the best hold on your galvanized steel surface.  A zinc chloride-based flux will get you the best flow onto the base metal.

A liquid flux that has an active chloride formation like Johnson’s Galvanized Steel Flux is a great choice for galvanized steel. Make sure to brush the flux wherever the solder makes contact.  The solder follows the flux.

3. Best Flux For Ornamental Copper Soldering

Like galvanized steel, the best flux for soldering ornamental copper is a zinc-chloride-based flux or a zinc-ammonium chloride liquid flux. You will get the best flow out of these flux types when soldering.

It is important to remove any extra flux after soldering so that it doesn’t corrode the finish or the ornamental copper soldering.  It can turn the copper green if not flushed off.

Clean the Flux And The Surface After Soldering

As important as it is to choose the right flux, it is equally important to clean any remaining flux residue after soldering.  You can just wipe down the surface with a damp cloth or flush it with clean water.  This can help prevent corrosion of the steel surface.

If you have any questions about which flux is best used for soldering your steel or copper project, please contact our technical support team. We have many different flux options from which you can choose. 


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