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5 Steps to Effectively Solder Stainless Steel

5 Steps to Effectively Solder Stainless Steel

Soldering is an effective way to join stainless steel in roofing applications. It is important, however, to choose the right temperature, heating unit, and flux to have a strong connection.

Although the oxide film that presents itself in stainless steel can make it more difficult to solder, it can be completed if the right techniques are used.

Below are 5 Steps to Effectively Solder Stainless Steel:

1. Prepare the Surface

Make sure to do a thorough clean of the steel surface, particularly in the joint area.  Remove the oil and grease with a cleaning solvent and use a stainless steel brush (or even a wire brush) to achieve a clean, metallic surface.  It’s best to solder right after cleaning before any other dirt or film attaches to the steel surface.

2. Choose an Aggressive Flux for Stainless Steel Soldering

Choosing the right flux is the most important step in soldering stainless steel.  You want to use an aggressive flux; rosin and no-clean fluxes will not work on stainless steel.  Try using a high activity, powerful phosphoric acid-based flux because of the tenacious oxides that are on the stainless steel surface.  These types of oxides can prevent the soldering from sticking to the steel surface. 

3. Pre-heat the Metal Surfaces With Your Heating Unit

Pre-heat both of the metal surfaces with either your torch or a soldering iron.  Use the heating unit to apply both pieces of the metal that you are trying to connect.  You want to leave your iron or torch on the metal until it is hot enough to melt the solder.  

4. Make Sure to Choose the Correct Solder

There are a range of tin-lead solders that can be used to solder stainless steels. It is generally recommended that the tin content should be more than 50% so that it has a greater joint strength.  High-tin solders will also match the stainless steels’ metallic color and won’t darken as much after being soldered.

5. Clean the Flux And The Surface After Soldering

Clean the flux off as well as the solder joints after you have finished soldering.  Wipe the surface down with a damp cloth or flush with clean water to prevent corrosion. 

When soldering steel, it’s always important to wear proper protection.  Make sure to wear gloves, safety goggles, coveralls and an air filter mask that allows proper respiratory protection.

If you have any questions about which flux is best for stainless steel, please contact our technical support team. We have many different flux options from which you can choose.