A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC

i vote brass bolts. I'm thinking of exhaust manifolds where steel
touches brass bolts. works well, in fact, better than steel bolts. I
have a zillion places where brass plumbing touches steel, brass does
fine.

Karl

wrote:
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC


How about a good epoxy or bonding agent ?

--
Steve W.

wrote in message
...
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC

You are probably over thinking it.
I've stuck brass locks, hinges, mailboxes and doodads on steel fences and
gates. Some have been out there for decades with no real issues.

That being said, I would minimize any direct contact by painting the steel
before assembly (using the paint like a nonconducting gasket). Design the
joint so it will not chip the paint off and use a steel bolt with a brass
nut. Designed like this, the bolts are likely to take the brunt of the
corrosion. Keep them cheap and easy to replace.

Paul K. Dickman

On Sun, 17 Jun 2012 23:32:55 -0700, wrote:

A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC

Yellow brass will dezincify in contact with plain steel, if the joint
is wet. Zinc will leach out of the brass and you'll have a weak copper
sponge where the brass once was. Threaded fasteners are the biggest
problem with this kind of galvanic corrosion, so brass bolts would be
about the worst. The near-contact area between the steel and brass is
directly related to the rates of corrosion. You also need direct
contact in some area. With two pieces of metal bolted together, you'll
have plenty of both.

But the steel *not* in near contact with the brass will rust first, if
it isn't protected. If you're covering the steel with POR 15, will it
be covered where the brass and steel are otherwise in contact?

It's tempting to suggest using a plastic tube in the bolt hole and
plastic washers under the head and nut, and coating both the steel and
the brass with a good barrier coating. but that may or may not solve
it, unless the barrier is perfect.

The cell to worry about is the zinc (in the brass) and the steel. If
you coat the steel (and maybe even the brass) with zinc chromate paint
or zinc-filled epoxy paint, the zinc in the paint wll be the
sacrificial anode -- for a while, at least. How many years does this
thing have to last?

With a very weak electrolyte, like rainwater, galvanic corrosion
probably will be slow. But when you bolt the pieces together, you'll
likely break through the barrier somewhere and that's where you'll
have trouble. A sheet of plastic between the two should help, but in
the end, you won't prevent galvanic corrosion unless you have perfect
isolation between the two metals.

Good luck. And better luck than I've had with metal on boats. I seem
to have a knack for setting up little electrical cells everywhere.
d8-)

--
Ed Huntress

wrote in message
...
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. ...

Michael Koblic,
Campbell River, BC

Test some samples:
http://en.wikipedia.org/wiki/Weather...ng_of_polymers

I once built an 80C, 80%RH environmental test chamber for a
semiconductor factory in Manaus, Brazil. We wondered if conditions
were worse within or outside the chamber.

I haven't seen significant corrosion on brass + aluminum + stainless
home-made pulleys on my TV antenna and remote chimney cleaner.

The chimney brush pulley is off for rearrangement of the mast so I
went out and took it apart. It's clean despite several years of rain
and wood smoke.

jsw

On Jun 18, 12:32*am, wrote:
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC

I saw the solution in a book on aluminum corrosion, bolting stainless
to alloy. In this case, you'd either use a brass bolt and nut with
the head on the brass side and an insulating washer under the nut or a
stainless bolt and nut plus insulating washer with the head on the
steel side. They did say paint made a useful insulator between parts,
as long as it was really weatherproof. So if you've got a good
coating with no holes on the steel part, you're probably good to go as
long as you don't get chips or holes in the paint. Another way to go
might be cold galvanize on the steel. Potential difference between
that and the brass is probably negligible.

Stan

wrote in message
...
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC

I have a 30 year old stainless pool filter tank with bronze wingnuts on
stainless threaded studs holding the cover on. Clorinated water is splashed
on it every other week. No visible corrosion so far. Although I do use a
little white grease on the threads, and bronze is not the same as brass.

The only corrosion are little pits in the s.s. where it makes contact with
the rubber gasket. I think this is where organic leaf debris sometimes gets
caught and creates acid conditions.

On Mon, 18 Jun 2012 16:22:41 -0700, "anorton"
wrote:


wrote in message
.. .
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. At this point
bolting them together seems the only realistic option (1/4"-20 or
5/16"-18, not written in stone). My main concern is the electrolytic
corrosion likely to result from the contact between the dissimilar
metals.

What would be the best way to minimize this? There are a few
permutations I have thought of:

1) Drill a hole through both and bolt together with stainless steel
nut and bolt.
2) Same, but use a brass bolt and nut.
3) Braze (:-0) a piece of brass thread to the brass part, hole through
the steel bit and a brass nut.
4) Thread the brass piece, hole through steel and use a stainless
steel bolt (no nut).

etc. etc.
Does thread locker protect from such corrosion?

The steel part will be painted with POR15.

Thanks,

Michael Koblic,
Campbell River, BC

I have a 30 year old stainless pool filter tank with bronze wingnuts on
stainless threaded studs holding the cover on. Clorinated water is splashed
on it every other week. No visible corrosion so far. Although I do use a
little white grease on the threads, and bronze is not the same as brass.

There is no reason for *galvanic* corrosion to appear with that
combination. Brass makes a galvanic cell with steel, chrome, or nickel
(as in your stainless) because of the zinc. And if the brass is 85%
copper -- in other words, red brass, or plumbinb brass, the zinc
generally won't leach out. Bronze can be almost anything, but most
bronzes are low in the low-potential alloying metals.

With stainless and chlorine, the biggest problem is stress corrosion.
That wouldn't be an issue here but it's hell on sailboat rigging.


The only corrosion are little pits in the s.s. where it makes contact with
the rubber gasket. I think this is where organic leaf debris sometimes gets
caught and creates acid conditions.

Possibly, or it's just holding the chlorine and water.

--
Ed Huntress

On Mon, 18 Jun 2012 19:43:32 -0400, Ed Huntress
wrote:

On Mon, 18 Jun 2012 16:22:41 -0700, "anorton"
wrote:



The only corrosion are little pits in the s.s. where it makes contact with
the rubber gasket. I think this is where organic leaf debris sometimes gets
caught and creates acid conditions.

Possibly, or it's just holding the chlorine and water.

Very likely the gasket is creating small pockets of stagnant
chlorinated water leading to crevice corrosion.
http://en.wikipedia.org/wiki/Crevice_corrosion

--
Ned Simmons

"Ed Huntress" wrote in message
...
On Mon, 18 Jun 2012 16:22:41 -0700, "anorton"
wrote:



There is no reason for *galvanic* corrosion to appear with that
combination. Brass makes a galvanic cell with steel, chrome, or nickel
(as in your stainless) because of the zinc. And if the brass is 85%
copper -- in other words, red brass, or plumbinb brass, the zinc
generally won't leach out. Bronze can be almost anything, but most
bronzes are low in the low-potential alloying metals.


--
Ed Huntress

Ed,

How is a brass-zinc connection? I'm no expert but it seems that
there would be no zinc leaching from the brass. If it's good, then
how about assembling the brass-steel joints with hot dipped steel
plates in the joint and use hot dipped steel hardware?
Art

In water systems, electromotive force causes ions to flow.
Must have plastic between the mix. Otherwise you get holes in the water
tank!

Martin

On 6/18/2012 6:08 AM, Karl Townsend wrote:

i vote brass bolts. I'm thinking of exhaust manifolds where steel
touches brass bolts. works well, in fact, better than steel bolts. I
have a zillion places where brass plumbing touches steel, brass does
fine.

Karl

"Ned Simmons" wrote in message
...
On Mon, 18 Jun 2012 19:43:32 -0400, Ed Huntress
wrote:

On Mon, 18 Jun 2012 16:22:41 -0700, "anorton"
wrote:



The only corrosion are little pits in the s.s. where it makes contact
with
the rubber gasket. I think this is where organic leaf debris sometimes
gets
caught and creates acid conditions.

Possibly, or it's just holding the chlorine and water.

Very likely the gasket is creating small pockets of stagnant
chlorinated water leading to crevice corrosion.
http://en.wikipedia.org/wiki/Crevice_corrosion

--
Ned Simmons

Interesting article, thanks. That would explain it. The debris helps create
pockets of stagnate clorinated water.

On Mon, 18 Jun 2012 09:40:18 -0400, "Jim Wilkins"
wrote:


wrote in message
.. .
A project of mine in the contemplative stage will probably require
joining a piece of brass to a piece of steel (about 1/2" thickness
each). Both will then be exposed to the elements. ...

Michael Koblic,
Campbell River, BC

Test some samples:
http://en.wikipedia.org/wiki/Weather...ng_of_polymers

[...]

Right. After considering all the responses (thanks!) I decided to cut
off a 1/4"-20 bolt, made a hole in the brass part, brazed the shank of
the bolt in it and drilled a hole in the steel part. I am hoping that
this way the brass-steel interface will be at a spot where the
corrosion matters least.

There are many other engineering issues to sort out on this project so
field testing will have to wait a bit :-)

Michael Koblic,
Campbell River, BC

"anorton" wrote in message
m...

"Ned Simmons" wrote in message
...
On Mon, 18 Jun 2012 19:43:32 -0400, Ed Huntress
wrote:

On Mon, 18 Jun 2012 16:22:41 -0700, "anorton"
wrote:



The only corrosion are little pits in the s.s. where it makes contact
with
the rubber gasket. I think this is where organic leaf debris sometimes
gets
caught and creates acid conditions.

Possibly, or it's just holding the chlorine and water.

Very likely the gasket is creating small pockets of stagnant
chlorinated water leading to crevice corrosion.
http://en.wikipedia.org/wiki/Crevice_corrosion

--
Ned Simmons

Interesting article, thanks. That would explain it. The debris helps
create pockets of stagnate clorinated water.

Oops, that would be "stagnant".

On Mon, 18 Jun 2012 18:25:36 -0700, "Artemus"
wrote:


"Ed Huntress" wrote in message
.. .
On Mon, 18 Jun 2012 16:22:41 -0700, "anorton"
wrote:



There is no reason for *galvanic* corrosion to appear with that
combination. Brass makes a galvanic cell with steel, chrome, or nickel
(as in your stainless) because of the zinc. And if the brass is 85%
copper -- in other words, red brass, or plumbinb brass, the zinc
generally won't leach out. Bronze can be almost anything, but most
bronzes are low in the low-potential alloying metals.


--
Ed Huntress

Ed,

How is a brass-zinc connection? I'm no expert but it seems that
there would be no zinc leaching from the brass. If it's good, then
how about assembling the brass-steel joints with hot dipped steel
plates in the joint and use hot dipped steel hardware?
Art

That's a good question, but I really can't help with an answer.

In theory, what you're saying sounds right. But brass and zinc have
electrical potentials (anodic indices) that are quite far apart
(around 0.8 V). The anodic index of brass is quite close to that of
copper. Although dezincification is a frequent issue with brass, you
still have to consider the potential of the copper.

If brass was a homogeneous material, the anodic indices would indicate
that the zinc galvanizing would be strongly sacrificial. But in terms
of preventing dezincification, there should be no corrosion or loss of
zinc on either side.

You'd have to ask someone who has real experience with it.

--
Ed Huntress