When mounting sweated copper pipe to wood framing using copper pipe straps, what type of fastener should be used? I have always been confused about what causes the galvanic reaction between copper and steel. Are drywall screws OK to use?

Thanks much for the advise.

TWC

There are two types of metals-ferrous which contains iron, known as steel or cast iron, and alloys which don't-copper, alumuminum, zinc, etc. The short lesson in galvanic reaction: When dissimilar metals are in contact with one another in the presence of an electrolyte, galvanic action occurs, resulting in the deterioration of the metal with the lower galvanic number. The electrolyte may be rain water running from one surface to another, or moisture from the air containing enough acid to cause it to act as an electrolyte.

Drywall screws are steel and should not be used. Instead use brass screws. Nails are also available that have a zinc plate brass irradite coating to be used with copper hangers. THese are available at any Menards, HD, Lowe's, or well stocked hardware. ALso, if your running the pipe along the wide part of the joist, these various types of fasteners work well. Sioux Chief (http://www.siouxchief.com/Frm_NS.cfm) FYI, many years ago I used steel screws on copper straps and never had a problem---but why chance it, use the proper fasteners. Problem with link-use it then go to "products" and look for "hangers and brackets."

, many years ago I used steel screws on copper straps and never had a problem---

We still use nails and have never had any problems in all the years we've been using them. Regards, Tom

Tom, I agree. I think some off these problems are overblown in order just to sell some specialty products :mad:

That is with all the good Florida salt air.

Thanks much for the feedback. Brass screws should be easy enough to get and use. Does stainless steel fall into the ferous camp for metal types? It isn't magnetic so I wasn't sure. Thanks for the explanation.

TWC

I would also suggest to use brass screws, brass don't require plating it is alloy of copper and zinc

http://appleinternationalenggworks.com/images/brass-screws-brass-fasteners-screws.jpg

Another solution is to put rubber between the different metals. This will prevent the metals from coming in contact with each other. Electrical tape works great.

Stainless steel is STEEL. If, as shader and speedball note, galvanic reaction occurs, it will occur between the ferrous and non-ferrous metals.

However, this process is complicated one. When we're talking about metals (ferrous and non-ferrous) with a direct path to EARTH (i.e. an electrical ground). There is an opportunity (if proper conditions exist to support a galvanic reaction) for corrosion to occur; dissimilar metals cause a very small electrical current to be produced by the chemical reation.

The opportunity for this small current to pass in the direction of the path to the WOOD is negligible. While wood contains moisture, it is NOT the path of least resistance; therefore, current is unlikely to flow in the direction of the path provided by the screws, nails, or whatever is holding these straps to the wood.

I'd use painted or coated screws, nails, or whatever, give it a rest, and move on.

BR,
Stew