Electrolysis - settle the \"debate.\"

hot_rod

but also the electrolyte. The reaction depends on how near the materials are on the list, but also the fluid in or around them.

It also has to do with the "relative area effect", the amount of metals. A copper bolt in a large sheet of iron, as opposed to an iron bolt in a large mass of copper. This is the example they use in the Copper Development Association materials, www.copper.org

The CDA has excellent reading material on this subject as it refers to copper, alloys, and dis-similar metals. Most of the reading material is free. Get a copy of the Copper Tube Handbook, for one.

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SpeyFitter

So what's the deal?

I've seen some questionable practices in the field that make me wonder. AT plumbing/gas school you learn a bit about electrolysis but you don't learn any real "lessons," and these types of lessons, anyways, are probably the ones you learn from an experienced Journeyman. I've seen, in heating systems (not done by myself) Copper MIP's screwed into Black Iron/Steel Tees for distribution. And the constant Brass/steel/brass fitting/pipe train. It seems that Brass or Bronze aren't affected so much by electrolysis as say Copper is.

For example, a lot of guys will screw a brass Union or a Brass Nipple right into a Stainless Steel Condensing Boiler tapping and then run Copper from there (off of the other side of the Brass Union or Nipple). Is this acceptable?

I can't understand why Watts touts the quality of their stainles steel radiant manifolds when they have all cast brass parts, adapters, etc, that are chromed/coated. I understand however, why you would want a heat exchanger to be stainless steel, but I think you see my point. Also, a lot of guys seem to think that Dielectric Unions aren't all they are cracked up to be.

Andrew Hagen_2

Galvanic Series

Galvanic corrosion is all about the relative positions of the metals on the galvanic series. The key is the spread in potential between the two materials. The big problem occurs typically when alumnium is coupled to copper. Others are close enough on the series that problems will very rarely be encountered.

Unknown

Dielectric unions on a closed system ?

Never used them and never seen them used . We take out many 40 , 50 , 60 year old boilers . Almost all of them have a threaded copper fitting in the cast or steel boiler or fittings . I've yet to see electrolysis buildup at the fittings . Oh I've seen leaks at the male or female adapters . But I can guarantee that was due to the fitting being soldered after it was tightned or it was just loose to begin with .

My opinion ? Dielectrics are never needed on a closed system . And open systems too .

Rich Kontny_3

Open Systems

Can be a problem when you lets say put a female adapter directly onto galvanized. Have seen countless examples of electrolysis. Another example would be galvanized plugs put into drip legs as drains in a copper system. They are attacked and eventually destroyed.

Closed systems are usually not a problem unless a lot of make-up water is needed. I used to prefer the old di-electric couplings over the unions.

Sissy

Just curious, but why is it that (just for an example) super stor requires a stainless steel well but then they include a 3/4 by 1/2 brass bushing in the package?

hot_rod

dp, sorryt

Andrew Hagen_2

Oxidation

I would guess that this is oxidation (rusting) and not corrosion in the case of open systems.

I have never seem galvanic corrosion in a heating system unless it had aluminum in it.

In my opinion, aluminum is just too reactive in general for use in a heating system.