NOKORODE

I want to open by stating that Nokorode® is still manufactured today. But do not take this as a product endorsement. This is a product more than a century old, so there's a lot of history to cover.  In their ads in 1913 the listed off their customers: New England Telephone & Telegraph, The D&W Fuse Company, The Johns-Pratt Co., The Sachs Co., and the Bryant Electric Company.  By 1920 it was Cadillac, Studebaker, Buick, Dodge, and Ford. More here and here.

It was originally made by the M. W. Dunton Company based at 65 Atlantic Avenue Providence, RI. It was bought out by the RectorSeal Company in 1998. It was an oil-based flux that supposedly also sealed solder joints against corrosion which they also sold as "soldering salts" in powdered form. The labels always read that it was patented in 1903. But what we find in the Official Gazette of the United States Patent Office from May 23rd 1903 is a patented "Label." It's Number 10,101, granted June 16th.

The paste was sold in tins, glass jars and more recently plastic buckets. On eBay I found a glass bottle of Nokorode flux. The wording and packaging indicate it was more of a liquid than a paste. It bore the following labeling:

"Nokorode flux will not deteriorate with age. takes the place of all other soldering fluxes, making it necessary to use only one flux for all kinds of work. Use this solution also as a dip to clean and tin soldering iron as well as a flux for the work. Do NOT use Sal Ammoniac."

That last bit is interesting. Sal ammoniac (aka salmiac), is a naturally occurring mineral composed of ammonium chloride (NH4Cl). It is the product from the reaction of hydrochloric acid and ammonia.  Today it's a common fertilizer. A hundred years ago it was also commonly used to clean the soldering irons used to make stained-glass windows. You can still buy it today, usually sold as a "tinning block." Why would we not want to use that with Nokorode?

Well Nokorode doesn't list the ingredients but the MSDS warning tells everything we want to know for this question. It says that Nokorode is lead-free (may not have been so in 1903) and "Contains: Zinc Chloride (ZnCl2) and Ammonium Chloride. Precautions: May cause irritation to eyes."  Nokorode already contains Sal ammoniac!   Note, that when that mixture is heated with a soldering iron this could produce fumes of zinc, chlorine and hydrochloric acid (HCl). These are all irritants. The ingredients of Nokorode turn out to be (mostly) petroleum jelly, zinc chloride and ammonium chloride.

So that also reveals why their instructions advise against using Nokorode on electronics. Both HCl and zinc chloride, (the actual flux agent) are corrosive to metals. That may not matter on a stained glass window with a thick metal joints, or automotive parts. But circuit boards and component joins are very thin, and more easily damaged by something with any corrosive effect on electrical connections. That's ironic. What's the anti-corrosive ingredient?  Probably the petroleum jelly.