Bolster seam corrosion

[Danvh]

I have several knives that I made with ATS34 and 416SS bolsters. Bolsters are pinned and silver soldered. I have noticed a small amount of corrosion in the seam of the bolster and ricasso. I clean it up with a chisel point brass rod but it comes back. Caused by the flux? Any suggestions on stopping the corrosion? Thanks

[Don Robinson]

Yep, it's not unusual to have the flux seep out of the joint.

Try soaking in a saturated solution of baking soda and water for several hours. Blow it out well with air pressure and spray WD40 into the joint afterwards.

[Don Cowles]

If you pin the bolsters, you don't need to solder them. That would solve the problem for future pieces.

[B.Finnigan]

You may also have a dielectric reaction going on. Many dis-similar metals when in a moist or humid enviroment will become a very weak battery and speed up the corrosion process. The Ph of the moisture makes a very big difference. I have always kept that in mind when putting together a knife. Stainless is going to react with any metal it is in contact with that is not stainless due to the nickel content in it. (example NiCd,Nimh batteries)

I am surprised that dielectric reactions are not discussed more on the knife making forums considering how many different metals are used. When I was in a basic machining class we had to learn about that right out of the chute.

In your situation it may be hard to tell if it is the flux and/or the dielectic process. Radio Shack has a small engineers pocket book series and the one titled "home science experiements" has a chart of which metal combinations produce the highest dielectric reaction. Some metals it is so low that it would not matter but other metals like zinc, copper and lead make a huge amount.

This is just a little tidbit to keep filed away, nobody wants premature corrosion on knife that could have taken 8-10 hrs to finish.

[Danvh]

Thanks for the help, I'll try soaking and see if that works. I do like the looks of the soldered bolster, but it is a pain. Next time I will see if I can get a seamles fit without soldering!