appiah4 wrote on 2025-06-16, 11:35:

So.. I have been doing electronic soldering for about 3-4 years now, and all this time I've been using Feldet's Lötfett solder p […]
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So.. I have been doing electronic soldering for about 3-4 years now, and all this time I've been using Feldet's Lötfett solder paste as flux for (mostly) desoldering and (to some extent) soldering.

Last night, I realized that it's not flux. It has flux, but is actually a zinc product that is meant for soldering copper pipes. Moreover people on the internet are pretty adamant that it is incredibly corrosive and will start to eat through electronics within months.

Obviously, I got concerned and dug into my storage. Nothing that I have soldered on has corroded. At all. And I'm not even meticulous about cleaning residue after soldering, so there's that.

Am I tempting fate here?

I can't answer your question, but the manufacturer also makes products meant for PCBs, so they might be able to answer you https://www.felder.de (or you will get a boilerplate answer of "this product is not meant for that use" and nothing more, but it's worth a try, IMHO).