Soldering Stainless Steel with Electronics Solder

Equipment, Tools & Supplies Soldering, Desoldering, Rework Products
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From time to time the question comes across my desk about soldering stainless steel wire, contacts, or other surface with the solder we carry here at DigiKey.

The issue with this question is not the fact that it can not be done, but that you need an acidic flux to solder stainless steel and for what should be obvious reason acid flux is not recommended in electronic applications.

Kester even comes right out on their site and says they do not recommend soldering to stainless steel in this document. (Soldering_to_Stainless_Steel.pdf (17.4 KB) ). David Scheiner goes on to talk about what your options are if you NEED to solder solder stainless steel you will have a couple options.

  • Use a mechanical connection
  • Use a plated stainless Steel
  • In a non-electrical/electronic situation (Mechanical) you could look at an acid Flux such as Kester 817.

So what is the secret to soldering stainless in electronics then? David also covers this and its simple there is no secret. If you have seen it you have likely either seen a nickel plated stainless which can be soldered with electronics solder or you have seen a joint that was soldered with an acidic flux. The problem with this joint is that the corrosion that allowed the solder to adhere to the stainless steel is slowing continuing to corrode the joint and will slowly dissolve the connection.

There are a few places out there that will say it can be done and will not mention that this is a short term solution. It this case the mechanical solution will likely be the best bet for a reliable connection.

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I read the “never use acid flux for electronics” on Kester’s website also. But I don’t understand the logic. Isn’t the real issue whether or not the flux can be cleaned off after soldering? How does the solder joint know whether it is being used for electronics or not? The same corrosion that will destroy an electronic solder joint will destroy a mechanical solder joint too if the flux residue is not cleaned off, won’t it?

Now, I will say you cannot clean flux residue that has wicked up into stranded wire, or probably between the insulation and solid wire. I can see how that will eat away at the wire over time. So, what I think would work is to tin the stainless with acid flux and a silver bearing solder, then wash off the flux residue. Then, solder the wire to the tinned stainless with electronic (rosin core) solder.

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Hello DGustavson,

Welcome to the community!

One factor for acid flux in electronics is it will wick up into stranded wire where it cannot be cleaned out like you suggest.

The other issue is you’re often talking about materials like hydrochloric acid, overall it causes corrosion on everything it touches so if any is left over after a cleaning process it will become a problem down the road.

The other issue with Acidic flux is it also suffers from the same problem as Rosin Mildly Activated in that it is hygroscopic, it’s going to absorb moisture which can become a problem in high impedance circuits.

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The term for a material that absorbs water from the air is “hygroscopic”.

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