A question about electrolisys

[Dan Mages]

I am in the process of finishing the roof on my shed. I am concerned about the potential for electrolysis. Is there any potential for problems using stainless steel nails on copper flashing?

Thanks

Dan

[Bruce Shiverdecker]

Dumb question, but is there a special reason for not using Copper or Brass nails?

Also, is the SS non-magnetic and copper-free?

Some stainless (Type 430 and lower grade) will RUST! Go figure.....430 is also magnetic. 302 Stainless is non-magnetic and won't rust.

This information comes from the Electrical industry, where we use both. Usually, when we use dis-similar metals, we coat them with an antioxident cream. Don't think that would work for you.

Just MHO.

Bruce

[Roger Kirkpatrick]

Bruce is right. Lots of grades of S.S.
I would think S.S. nails would be make from the cheap stuff.
I would use copper nails.

[Dan Mages]

I have 1.5 inch copper nails, but they not long enough to go through the copper, ridge vent, cedar shingles, and into the substrate below. I will verify if the nails I have are 305 or 404. The reason I am using cedar nails is that they will not cause staining on cedar shakes and siding like galvanized nails. I also have some aluminum nails, but they are much too weak to be used. I tried a box and got about 30% scrap out of them.

Dan

[BRAD CHAMNESS]

Hey Dan,
I'm new to this forum but looks like a nice place to learn about woodworking here.I'm a Sheetmetal worker by trade and work with these metals,I think you would be fine with the stainless nails because they are made to be used outside and not rust and discolor, check with a magnet to be sure there is no steel in them if they don't stick I think you would be safe to use them.

[Dan Mages]

ummm... Gulp? It looks like the stainless steel I picked up at the Borg are magnetic. However, the 2 38" stainless trim nails I got at the other borg are not magnetic. I may have to crawl back up there. Take off the shingles, and redo them. :(

Dan

[Aaron Koehl]

oh no.. that really stinks.

[Greg Mann]

ummm... Gulp? It looks like the stainless steel I picked up at the Borg are magnetic. However, the 2 38" stainless trim nails I got at the other borg are not magnetic. I may have to crawl back up there. Take off the shingles, and redo them. :(

Dan
Dan,

Just because it is magnetic does not mean it will rust or corrode at will. Before you tear into your work why don't you do a little experimenting with a few nails in a scrap shingle, exposing them to water and see what happens. They still are stainless steel after all, just not the most corrosion free grades. They are just less corrosion resistant relative to 300 (non-magnetic) grades, but certainly more corrosion resistant than many other materials.

Greg

[Dan Mages]

Welp. I am not concerned about the reaction between the shingles and the nails. I am worried about the reaction between the nails and the copper. It is only about 25 shingles that are affected. It should take about 30 minutes to an hour to fix. I just hate climbing my roof with the 30 degree pitch.

Dan

[BRAD CHAMNESS]

Dan, not sure I'd climb back up there to redo it even though the nails were magnetic there still stainless plated and IMO would do an adequate job of providing a barrier between the different metals.

[Hal Flynt]

I have learned more about fasteners materials and uses from Jamestown Distributors than about anywhere else.

Metal compatability; http://www.jamestowndistributors.com/decoder_compmetals.asp

Main Fastener page:
http://www.jamestowndistributors.com/eserv/eclipse.ecl?PROCID=WEBDISP.WOEB.MAIN&ID_1=1&CLEV=MORE&TRACKNO=J1684588752

P.S. Their Nicholson Rasps ar 45% off now, both the 49 & 50

[Dave Richards]

The thing to find out is the half cell potential of the stainless steel you have and compare it to copper. I couldn't find any half cell potentials for stainless during a quick search on Google but my Biomed textbook lists the following:

Iron -0.44V
Copper +0.34V

Put the two in an electrolyte and you have a voltaic cell with an output of .78V. Not real high but enough that over time, the metals will indeed react and cause problems. I don't know how much iron there is in your stainless. There is some nickel which would reduce the differential a little.

Rainwater will make an ok electrolyte.

I think you should buy a handful of longer copper nails and use those.

[Dan Mages]

I think I will be fine. I will check on it in the spring and see how it fares.

Dan

[Dale Thompson]

Dan,
Anytime that you have dissimilar metals and an electrolyte you are going to have a voltaic migration from one metal to the other (i.e. corrosion). If the rain in your area is distilled water, you will have no problem. Pure water doesn't conduct electricity. On the other hand, you probably don't have this situation. If I were putting a roof on my cardboard house and if the roof was copper, I'd use copper nails. Stainless steel has too many meanings. Besides, stainless steel has nothing to do with the "Electromotive Chart". That is what will determine whether you will have a rust problem or not.

I don't want to cause a panic but just think of what happens when you connect copper water pipe to "galvanized" pipe. :eek: :) Just a thought! :)

Dale T.