Bonding bronze bolts with epoxy

Bonding bronze bolts with epoxy

Post by Al Gunth » Sun, 29 Nov 1998 04:00:00


In the Gougeon Brothers book on boatbuilding, they devote a section on
bonding stainless steel bolts with epoxy. I had planed to bond the bolts
on my skeg in similar fashion an so I set up a test. I drilled a slightly
oversized hole in a piece of ash, which I intend to use for my skeg
floors, cleaned up a piece of the 1/2" silicon-bronze rod which will be
used for my bolts, and epoxied it into the hole. After several days in a
warm place, I inspected the setup. The epoxy that is on the wood has set
up nearly glass hard as normal, but all the epoxy touching the bronze is
gummy and I can peel it off with my fingernail. The gummy epoxy has turned
blue, just like copper would with exposure to salt. I can also see blue in
the epoxy between the wood and the bronze.

Anybody know why epoxy would react this way with bronze?
--
Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W

 
 
 

Bonding bronze bolts with epoxy

Post by Dave Carnel » Mon, 30 Nov 1998 04:00:00

Most epoxies contain amine hardeners that are related to ammonia.  Put some
household ammonia on a bronze bolt and see what happens.  Ammonia is very
reactive with copper alloys.  A 1:1 epoxy will probably have a polyamide
hardener and may not give that reaction.  I don't have any to try.

Dave Carnell   <http://home.att.net/~DaveCarnell>

Quote:

> In the Gougeon Brothers book on boatbuilding, they devote a section on
> bonding stainless steel bolts with epoxy. I had planed to bond the bolts
> on my skeg in similar fashion an so I set up a test. I drilled a slightly
> oversized hole in a piece of ash, which I intend to use for my skeg
> floors, cleaned up a piece of the 1/2" silicon-bronze rod which will be
> used for my bolts, and epoxied it into the hole. After several days in a
> warm place, I inspected the setup. The epoxy that is on the wood has set
> up nearly glass hard as normal, but all the epoxy touching the bronze is
> gummy and I can peel it off with my fingernail. The gummy epoxy has turned
> blue, just like copper would with exposure to salt. I can also see blue in
> the epoxy between the wood and the bronze.

> Anybody know why epoxy would react this way with bronze?
> --
> Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W


 
 
 

Bonding bronze bolts with epoxy

Post by Dave Carnel » Mon, 30 Nov 1998 04:00:00

Quote:

> Most epoxies contain amine hardeners that are related to ammonia.  Put some
> household ammonia on a bronze bolt and see what happens.  Ammonia is very
> reactive with copper alloys.  A 1:1 epoxy will probably have a polyamide
> hardener and may not give that reaction.  I don't have any to try.

> Dave Carnell   <http://home.att.net/~DaveCarnell>

I forgot to mention that the uncured resin next to the bronze bolt is the result
of hardener reacting with it to make the blue color so that the mix is deficient
in hardener next to the bolt.

Dave

Quote:


> > In the Gougeon Brothers book on boatbuilding, they devote a section on
> > bonding stainless steel bolts with epoxy. I had planed to bond the bolts
> > on my skeg in similar fashion an so I set up a test. I drilled a slightly
> > oversized hole in a piece of ash, which I intend to use for my skeg
> > floors, cleaned up a piece of the 1/2" silicon-bronze rod which will be
> > used for my bolts, and epoxied it into the hole. After several days in a
> > warm place, I inspected the setup. The epoxy that is on the wood has set
> > up nearly glass hard as normal, but all the epoxy touching the bronze is
> > gummy and I can peel it off with my fingernail. The gummy epoxy has turned
> > blue, just like copper would with exposure to salt. I can also see blue in
> > the epoxy between the wood and the bronze.

> > Anybody know why epoxy would react this way with bronze?
> > --
> > Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W


 
 
 

Bonding bronze bolts with epoxy

Post by Al Gunth » Mon, 30 Nov 1998 04:00:00

Quote:

> Al, I've epoxied bronze into fiberglass many times and never the reaction you
> described.  Could it be a reaction with the sap in the wood?
> --
> Bob Brake


Like I mentioned, the epoxy which was on the wood alone, cured glass hard.
The only problem was in the first few thousands of an inch next to the
bronze. I expect it may have to do with the type or brand of epoxy. This
was System Three's Laminating epoxy. I might try a coating of their Clear
Coat and see how that works.
--
Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W
 
 
 

Bonding bronze bolts with epoxy

Post by Patrick Crocket » Mon, 30 Nov 1998 04:00:00

Were I you, I'd e-mail the Sys3 guys directly and ask -- they've always
seemed like friendly and helpful folk in the past.  If you do and they have
an interesting answer, please post it.  I've certainly not noticed blueness
on  top of bronze fasteners epoxied over, or under oarlock sockets I set in
place with epoxy.

Patrick Crockett

Quote:
>Like I mentioned, the epoxy which was on the wood alone, cured glass hard.
>The only problem was in the first few thousands of an inch next to the
>bronze. I expect it may have to do with the type or brand of epoxy. This
>was System Three's Laminating epoxy

 
 
 

Bonding bronze bolts with epoxy

Post by Al Gunth » Mon, 30 Nov 1998 04:00:00

Quote:

> Were I you, I'd e-mail the Sys3 guys directly and ask -- they've always
> seemed like friendly and helpful folk in the past.  If you do and they have
> an interesting answer, please post it.  I've certainly not noticed blueness
> on  top of bronze fasteners epoxied over, or under oarlock sockets I set in
> place with epoxy.

> Patrick Crockett

Good suggestion. I had lost Kern's address but have since dug it out of
dejanews and have forwarded the question to him. I also mentioned that I
had cleaned the bronze with *** first, in an effort to remove any
possible oil on the surface. The bronze came shiny and new and had an oily
feel to it.
--
Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W
 
 
 

Bonding bronze bolts with epoxy

Post by Gary Zwissle » Tue, 01 Dec 1998 04:00:00

Al,

I've done the exact same thing as you, but never had that result.  I'd
be real interested to hear what Kern thinks the cause might be.  My
stern bearing is bolted to the after end of my deadwood this same way.
The installation came out great.  I hope I don't have something to worry
about.  About the only thing I did differently was wash the bronze in
acetone (rather than ***) and brush vigorously with a stainless
steel brush.  My bolts are 1/2" x 3.75", set in holes 3/4" x 2".
They've withstood installing the stern bearing, and tightening the bolts
to full torque with no problems.

Gary Z.

Quote:


> > Were I you, I'd e-mail the Sys3 guys directly and ask -- they've always
> > seemed like friendly and helpful folk in the past.  If you do and they have
> > an interesting answer, please post it.  I've certainly not noticed blueness
> > on  top of bronze fasteners epoxied over, or under oarlock sockets I set in
> > place with epoxy.

> > Patrick Crockett

> Good suggestion. I had lost Kern's address but have since dug it out of
> dejanews and have forwarded the question to him. I also mentioned that I
> had cleaned the bronze with *** first, in an effort to remove any
> possible oil on the surface. The bronze came shiny and new and had an oily
> feel to it.
> --
> Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W

 
 
 

Bonding bronze bolts with epoxy

Post by KernHe » Wed, 02 Dec 1998 04:00:00

Quote:

>The epoxy that is on the wood has set
>up nearly glass hard as normal, but all the epoxy touching the bronze is
>gummy and I can peel it off with my fingernail.

This seems to be a reaction to a specific amine in the System Three hardeners.
We haven't tried Clear Coat.  One solution is to coat the bronze with a thin
film of five-minute epoxy and once cured pot it with the System Three epoxy.
Frankly, we are aware of the problem but haven't put much effort into studying
it.

W. Kern Hendricks
System Three Resins, Inc.
Seattle, WA  98107
Technical Support:  206/782-7976
Orders/Literature Only:  800/333-5514
FAX:  206/782-4426

web site:  http://www.systemthree.com

 
 
 

Bonding bronze bolts with epoxy

Post by Al Gunth » Wed, 02 Dec 1998 04:00:00

Quote:


> This seems to be a reaction to a specific amine in the System Three
hardeners.
> We haven't tried Clear Coat.  One solution is to coat the bronze with a thin
> film of five-minute epoxy and once cured pot it with the System Three epoxy.
> Frankly, we are aware of the problem but haven't put much effort into studying
> it.

My crude test revealed 700 psi shear and the rod pushed out of the epoxy,
leaving the epoxy in the hole in the wood. I've redone the test using
Clear Coat and will test in the same manner which will at least give me a
good comparison. I'm not sure what shear value ash can be expected to hold
when it's surrounding something, but I would think it should be higher
than the 1950 psi value I find in tables. Cured Clear Coat, I'm presuming,
should be good for over 7,000 psi in shear.

If I don't get a wood failure this time, I'll try the five-minute epoxy.

Thanks,
--
Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W

 
 
 

Bonding bronze bolts with epoxy

Post by Mark Anders » Wed, 02 Dec 1998 04:00:00

Quote:

>I also mentioned that I
> had cleaned the bronze with *** first, in an effort to remove any
> possible oil on the surface. The bronze came shiny and new and had an oily
> feel to it.

***s are generally polar molecules, and oil generally isn't, so
*** may not be a great cleaner in this situation.  How about a
repeat test using uncleaned bronze, cleaned with ***, and cleaned
with acetone, which is not a polar molecule?

--
Mark Anderson
Riparia
"The trouble with good ideas, is that they soon turn into
 alot of hard work."  Anon.

 
 
 

Bonding bronze bolts with epoxy

Post by Patrick McCrar » Wed, 02 Dec 1998 04:00:00

Al,

You've probably already tried this, but rather than using a stud, use a
regular hex-head bolt, (or add a nut).  With the inverted boalt head you've
increased the surface area to over 3 times that of a straight stud, plus the
added effect of an anchor mechanism.

re: http://www.usamarine.net/stud.gif

Also under cutting the parent material, to give a reverse lip will further
strenghten the application.

Regards,
Patrick
http://www.usamarine.net/cc/

Quote:



>> This seems to be a reaction to a specific amine in the System Three
>hardeners.
>> We haven't tried Clear Coat.  One solution is to coat the bronze with a
thin
>> film of five-minute epoxy and once cured pot it with the System Three
epoxy.
>> Frankly, we are aware of the problem but haven't put much effort into
studying
>> it.

>My crude test revealed 700 psi shear and the rod pushed out of the epoxy,
>leaving the epoxy in the hole in the wood. I've redone the test using
>Clear Coat and will test in the same manner which will at least give me a
>good comparison. I'm not sure what shear value ash can be expected to hold
>when it's surrounding something, but I would think it should be higher
>than the 1950 psi value I find in tables. Cured Clear Coat, I'm presuming,
>should be good for over 7,000 psi in shear.

>If I don't get a wood failure this time, I'll try the five-minute epoxy.

>Thanks,
>--
>Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W

 
 
 

Bonding bronze bolts with epoxy

Post by Al Gunth » Wed, 02 Dec 1998 04:00:00

Quote:

> You've probably already tried this, but rather than using a stud, use a
> regular hex-head bolt, (or add a nut).  With the inverted boalt head you've
> increased the surface area to over 3 times that of a straight stud, plus the
> added effect of an anchor mechanism.

> re: http://www.usamarine.net/stud.gif

> Also under cutting the parent material, to give a reverse lip will further
> strenghten the application.

> Regards,
> Patrick
> http://www.usamarine.net/cc/

My application is different. I'm bonding six bolts to the skeg floors
which will be bonded to the hull and two of the 6 floors will be bonded to
a bulkhead. These aren't studs, they are rod which will be threaded on
each end and bedded in 3M-5200 in the skeg itself. There are nuts on the
skeg shoe at the bottom to allow removal and nuts on top of bearing plates
which sit on the floors inside the hull. The object of the epoxy bonding
to the floors is to pick up compression loads as the bronze is stiffer
than the wood which will make for a stiffer skeg and better support for
the rudder.
--
Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W
 
 
 

Bonding bronze bolts with epoxy

Post by Al Gunth » Thu, 03 Dec 1998 04:00:00

Quote:

> This seems to be a reaction to a specific amine in the System Three
hardeners.
> We haven't tried Clear Coat.  One solution is to coat the bronze with a thin
> film of five-minute epoxy and once cured pot it with the System Three epoxy.
> Frankly, we are aware of the problem but haven't put much effort into studying
> it.

In my case, Clear Coat seems to work fine. I tested a 3/4" piece of
Silcon-Bronze that had been Clear Coated in to a 1" piece of ash after a
24 hour cure. I estimate it took around 4 tons of force to break the bond
and I'm sure that a 4" bond in ash has more holding power than a bronze
nut.
--
Al Gunther, Kingston, WA  <---- 47 52.7'N, 122 30.9'W
 
 
 

Bonding bronze bolts with epoxy

Post by KernHe » Thu, 03 Dec 1998 04:00:00

Quote:

>In my case, Clear Coat seems to work fine. I tested a 3/4" piece of
>Silcon-Bronze that had been Clear Coated in to a 1" piece of ash after a
>24 hour cure. I estimate it took around 4 tons of force to break the bond
>and I'm sure that a 4" bond in ash has more holding power than a bronze
>nut.

There you go.  Your post illustrates a point that readers may have picked up
from my posts (and our literature) over the past couple of years:  When in
doubt check it out yourself.  Self-reliance seems to be a lost art in these
days of instant gratification.  Anytime you "mix" materials from two
manufacturers you may be creating a new system and it is the responsibility of
the person creating the system to make sure that it will accomplish his goals.
A mixture can consist of a bronze bolt and epoxy resin such as in Al's case or
an epoxy resin coating on wood and a particular paint or varnish as has been
recently discussed elsewhere in this newsgroup.

Making a simple model of the "system" you plan will most certainly tell you if
something WILL NOT work and by deduction give you a strong sense of its
probable success.  If you go ahead anyway into this uncharted territory you
will be doing this test anyway.  The difference will be one of scale:  Will you
be throwing away a small s***of epoxy coated plywood with some undried paint
or will you learn the same thing and have hours to think about it as you try to
salvage your entire project?

W. Kern Hendricks
System Three Resins, Inc.
Seattle, WA  98107
Technical Support:  206/782-7976
Orders/Literature Only:  800/333-5514
FAX:  206/782-4426

web site:  http://SportToday.org/