Now, as for more abusive treatments? I use a molten salt bath to prepare enameled wire with insulation that is not solderable. One can also use nitric acid, but that has gotten very hard to buy as it can also be used to make explosives. As for the molten salt, try NaOH or KOH in a steel/iron pot. Adding sodium nitrate (NaN03), readily available) makes it much more active. In practice, I use a small steel block with a larger hole in the center (e.g., 1/2" to 3/4" dia.) and a smaller hole for a TC or thermometer.
Can also be done in a stainless steel spoon, if you don't mind looking like a crack fiend (heavy /s..).
Have also tried potassium chlorate, which oxidizes organics viciously, but does nothing for the metal; my current favorite is to simply burn the wire, charring and oxidizing the organics, then dipping in molten NaOH to clean the metal. The resulting sodium cuprate (and various carbonates and hydroxides as molten NaOH absorbs CO2 rapidly in air, from flame, etc.) washes away completely, leaving a rough pickled surface that accepts solder well. The momentary high temperature also anneals the wire, for whatever that matters (which, if it makes it too soft, consider additional strain relief near the joint, etc.). Obviously, this isn't feasible for fine stranding, which burns away / melts into a blob too quickly, and nitrate or a nitrate/hydroxide blend, is likely better.
Absolutely not. Chloride ion contamination + ambient humidity, over any significant period of time is corrosion death for thin copper. Its the same reason no-one sane uses acid zinc chloride flux (aka: killed spirits of salt, or plumbers flux) for electronics: You cant get all the acid chloride contamination out of the tiny crevices in stranded wire or under components on circuit boards. See: https://en.wikipedia.org/wiki/Bronze_disease
Can confirm, copper and chloride are strong but sometimes inconvenient friends. I once had some bus wire that I annealed, pickled (in HCl) and hot dipped in tin, and they still grew green rotty spots, I assume either in pinholes or bumps on the tinned surface, or due to trapped material that continued to react, expand, and penetrate the tin.
1/ High temperature wire may have a silver plating to reduce oxidation. Identify by very bright silver finish, hard to scrape off.
Very common in stranded Teflon and fiberglass covered wire used in appliance automotive, heaters, industrial. Also some Kynar wire wrap wire has this.
Better to crimp a lug or splice as soldering is very difficult. but silver solder and a hot iron or solder pot might work.
Eh? Silver is extremely solderable; bright silver hardly needs rosin, it's pretty impressive really. Once tarnished, it can be quite difficult however. I suppose more or less, because Ag2S is the dominant form of tarnish, and metal sulfides have particularly low solubility in, pretty much everything, really. It takes time for rosins to break that down.
If you're confusing it for nickel plating though -- that stuff is a bitch to tin, to not mince words. A more active flux is required to do much of a job with it; regular rosin does work eventually, but in that time you've wicked so much rosin up the cable, impossible to clean out, that it probably won't last very well over time (and assuming you needed the temperature rating for a reason).
Both platings are commonly used with PTFE insulation. I still have some scraps of MIL-something, mineral-filled PTFE jacket, multistrand nickel-plated copper cable, which is great when you need a lot of temperature handling and stuff, but if you don't have a crimp to make connections, good luck. I have tinned the stuff before, uh, mostly, it still looks pretty thin -- but it's definitely not something you want to rely on.
Nickel plated wire will never solder, unless you use some fine sandpaper to remove the nickel coat. Generally the underlying metal is a stainless steel alloy, so it only works with crimp connections that make a gas tight join. Silver plate solders really easy, the nickel does not. No way to solder that nickel high temperature cable at all reliably, you always crimp it.
Generally--? Nickel plated copper with PTFE might be more common overall, but if you're talking about a particular market segment, like, if you've only worked with heating elements, those alloys -- stainless, nichrome, Kanthal, etc. are commonly used, yeah.
Hmm, nickel plating on those, I've never heard of, but not to say I doubt their existence. It would be one way to make it more solderable, considering anything chrome-bearing basically needs fluorides to beat back that tough of an oxide... On that note though, I do see some copper-plated materials available / in existence, which would solve that issue extremely well. *shrug*
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Not mentioned so far:
Some plain PVC jacketed tin-plated wire just does not solder.
I have some light blue stuff that is this way. Have seen it in old TV sets too (they used wire wrapping instead; maybe it wasn't very solderable even when new..!). Best solution is simply abrade off the plating. Again, as said, acid is too risky, and if you don't have any stronger activated rosins, that's about it.
There's also various kinds of corrosion that happen within the cable, give or take environmental conditions. I have a number of leads that've, probably sat too close to some chemical experiment I did or something like that, and probably a combination of chlorine fumes, and and other oxidation, light exposure, handling/touch, and plain old time, have done a combination of displacing or hydrolyzing the PVC plasticizer, oxidizing the copper (it's brown to black inside, maybe green towards the ends if not joined to something), and dissolving/complexing it (there's brown goo inside). Most common plasticizers are phthalates, which after hydrolysis, can form copper complexes (salts, namely), and the resulting isononol or etc. would explain the "goo" component. Also since decomposition liberates an acid (albeit a mild one), this decomposition can be autocatalytic (once triggered, it keeps going).
Tim
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