Hi. I just made some homemade killed acid soldering flux. But, instead of using old carbon-zinc battery cans, I used galvanized pipe ends. This stuff works great, and is very active. It is good for steel and copper.

There is, however, something I have been wondering about. Galvanized pipe coatings contain cadmium, either as a tramp or as an intentional underlayer to enhance corrosion protection. Sometimes this can be seen as a yellow deposit when heated. I looked on the www to find cadmium contents, and found a world of information, but nothing on content. There was even an engaging chemical forensics page. Does anybody know about content and potential hazards?

Both sources of zinc are free. But the galvy pipe leachings are slightly better than free. :)

Cadmium tends to be a pretty potent poison. You might want to check on your life insurance and make sure everything is up to date.

The zinc is also quite deadly... maybe you should page your life insurance agent right away?!

you should read the safety sticky on these hazards soon. They are located at Safety First at iForge

Beware yellow snow and run from that yellow deposit. Zink and cad are TOXIC
Ken

Hi everybody. Thanks for the warnings. I reviewed the sticky on the hazards of zinc and cadmium. It is fairly generic for cadmium, and it does not list the main pathways by which cadmium is adsorbed in the body. Looking around the WWW, some sites say ingestion from water which has corroded galvanized pipes, and others say cigarettes. I am much more likely to believe the latter, since much of ingested cadmium simply passes through the gut.

Recently, the local university, fearing the risks of cadmium poisoning, gave away all their cadmium containing silver solder. It was free for the taking, and I picked up a few coils of it. From what I read, overheating is the main risk. I use hi-cadmium content aluminum solder, which is nearly half cadmium. You have to be really careful about overheating this stuff, but they still sell it at the welding shop. Bicycle frame builders have used cadmium containing solders for years with few ill results if the simple precautions have been applied. And, people brazing with brass have gotten poisoned by tramp cadmium by brazenly ( ) overheating the filler. I asked Bernzomatic how much tramp cadmium was in their brass rod that they sell in big box stores, and they got all skittish. Don't overheat it, and you should be OK.

I am a little leery about this homemade flux, since it is really hard to tell how much cadmium is in it. By the way, most flux for soldering plumbing pipe contains a lot of zinc chloride. And, it is fairly safe. It is difficult to overheat, just because of the way the joints are set up. You are more likely to start a fire with the soldering torch than to get zinc fume fever from this stuff.

What exactly is killed acid solder?

And yes over heating lead or cadmium containing is bad, due to the whole metal fume thing.

Is there a good flux for soft soldering (lead free solder) brass to steel? I use propane, for heat, and have had no luck soldering brass bolsters to steel knife blades. The solder just doesn't stick to the steel with regular plumbing flux. I am going to get some better lead free solder, the cheap stuff just doesn't flow worth an old shoe.

What alloys are your knife blades?---makes a difference on what fluxes work well.

"Killed acid FLUX" is zinc chloride made by dissolving zinc in HCl until it's "killed" (neutralized). One of my old "Farm Shop Manuals" discusses it.

Thanks Thomas for answering. This flux works great for soldering steel to brass. The plumbing flux has a lot of grease in it. It works fine for copper to copper or brass to copper. But, for some reason, it does not work well on steel. The solder doesn't seem to spread. The killed acid flux, even with a lot of red rust in it, works just great for steel. The solder spreads well. I like it. It might work even better if it was left a little acidic, but then it is more corrosive.

Thomas and evfreek, thanks for that, it seemed like the plumbing flux burned off and kept the solder from sticking. As for alloy its whatever they make leaf and coil springs from.

Would alloy actualy make a significant difference in soft soldering?

...

Would alloy actualy make a significant difference in soft soldering?

Hi CBrann. I would think that it does. But I have not tried. I know that alloy does make a difference when soldering aluminum. Some alloys can be soldered with simple flux and a little scratching. Others need the aggressive trifluoroborate flux.