"Ed Huntress" wrote in message news:...

"Michael Koblic" wrote in message
...
I am trying to glue a 0.006" brass foil to a mild steel plate. I have done
it in the past but forgot what I used (note to self: keep better
records!).

I have run several small scale trials and for some reason the results are
dismal: JB Weld, Devcon 2-ton, E6000, household Goop, Jelly
cyanoacrylate - the brass just peels off like I am using school glue!

I abrade both surfaces. I clean with acetone. I leave to cure for 24
hours at least (that includes the CA). Nada!

What am I missing? BTW it is the *brass* side of things where the glues
do not stick.

--
Michael Koblic,
Campbell River, BC

You have several issues here. First, as others have mentioned, copper and
its alloys develop a thin, weak, invisible oxide layer in seconds. Second,
JB Weld is filled and is not formulated as an adhesive, but rather as a
kind of hybrid filler/so-so adhesive. Cyanoacrylate and epoxy, unless
they're formulated for high peel resistance, have terrible resistance to
peel and cleavage, which is what you're going to run into with material
that's 0.006" thick.

Everything is working against you. g

Tawwwwm suggested a laminate adhesive. That will cure a lot of ills,
because it doesn't get real hard and it does very well with peel loads.
Its ultimate strength isn't particularly high but it may well produce the
strongest bond in this case because most other adhesives that are stronger
are also less peel-resistant.

But here's a suggestion to help get a stronger bond, no matter what you
use (except with cyanoacrylate -- I don't think you can work fast enough
to beat its cure time). Use the "scratch-in" method, which works with the
other miserable metals that develop instant oxides -- stainless, aluminum,
magnesium, and, in my limited trials, copper.

The idea is to wet-sand the piece with a piece of fine sandpaper, wet-dry,
or Scotchbrite, with the part and the sanding medium soaked in adhesive.
You don't have to cut deep; just clean the surface well. The key is to
never let the part be exposed to air once you start. Keep it covered with
adhesive. If it produces too much sanding sludge, wet a rag with adhesive
and wipe the part, making sure you keep it wet and NEVER let air touch it.
If you wipe it dry, re-sand and do it all over again.

I haven't used the vicious laminate adhesive for years, but my
recollection is that it dries very, very fast. You'll have to work quick.
And work outdoors. You'll be slopping it around and the solvent is horrid.

Do the same with the other piece you're adhering to, if you can (not if
it's wood). Then put them together wet -- or, in the case of laminate
adhesive, when they've reached the proper tacky stage.

You'll get a good mechanical bond, and it's one of the few ways to also
get a chemical bond with these metals. In volume production they use a PAA
anodize on aluminum, but the scratch-in method works about as well, in my
experience, and I've had success with it on other metals. I ran some
crude, informal tests with it back around 1980 when I was writing about
adhesive assembly for _American Machinist_.

I got this tip from the guys who founded the WEST System. They're epoxy
experts. They were NOT dealing with peel loads; how well you do with that
will depend mostly on your adhesive. No over-the-counter,
room-temperature-cure epoxy is very good in peel. Most cyanoacrylate is
dismal in that department, but there are some sort of gummy ones that may
do it.

Good luck!

--
Ed Huntress

I forgot one important thing: If you want to try epoxy, keep in mind that
its maximum strength, particularly in metal-to-metal bonding, is achieved
with a bond layer approximately 0.002" thick. Any thinner, and the strength
goes to pot -- especially peel/cleavage strength. I often leave a little
sanding grit in the joint to be sure I'm not starving it out.

It can tolerate a thicker layer, up to around 0.006" or so, without losing a
lot of strength.

--
Ed Huntress

On Thu, 08 Jul 2010 11:58:06 -0400, Ed Huntress wrote:
"Ed Huntress" wrote
"Michael Koblic" wrote
I am trying to glue a 0.006" brass foil to a mild steel plate. I have
done it in the past but forgot what I used (note to self: keep better
records!).

I have run several small scale trials and for some reason the results
are dismal: JB Weld, Devcon 2-ton, E6000, household Goop, Jelly
cyanoacrylate - the brass just peels off like I am using school glue!

[snip re abrade and clean with acetone]

You have several issues here. First, as others have mentioned, copper
and its alloys develop a thin, weak, invisible oxide layer in seconds.
Second, [...]
Everything is working against you. g
....

Maybe you sent it out to a plating shop and then suppressed the memory

Couple lists of BC platers:
http://www.macraesbluebook.com/search/product_company_list.cfm?prod_code=5800100&region= British%20Columbia-BC
http://www.profilecanada.com/category.cfm?cat=3471_ElectroplatingPlatingPolishi ngAnodizing-and-Coloring&pos=215&slid=0
Might also be worth inquiring at local shop North Island Chrome Inc, first
item on http://www.yellowpages.ca/search/si/1/Plating/Campbell+River+BC

--
jiw

"Ed Huntress" wrote in message
...


[...]

I forgot one important thing: If you want to try epoxy, keep in mind that
its maximum strength, particularly in metal-to-metal bonding, is achieved
with a bond layer approximately 0.002" thick. Any thinner, and the
strength goes to pot -- especially peel/cleavage strength. I often leave a
little sanding grit in the joint to be sure I'm not starving it out.

It can tolerate a thicker layer, up to around 0.006" or so, without losing
a lot of strength.


Thank you and all the others.

I was not aware of copper being a problem with glues.

I have your "scratch-in" method saved in my works folder from last time you
mentioned it here and was going to try it next. The only reason I was
hesitating is that the reverse side of the brass foil is supposed to look
intact and in the past any speck of dust or other mechanical disturbance
produced blemishes which were impossible to get rid of. However, I guess now
is the time to try again, very carefully.

As for the optimum layer of glue I wonder if going to a coarser abrasive
would help by producing more pronounced peaks and valleys on both sides of
the material - perhaps just on the steel side.

I was going to try the solder paste method as a last resort. I have played
with a couple of different kinds and I don't like them for ordinary
soldering/silver soldering. However, this may be the right place for it.

--
Michael Koblic,
Campbell River, BC

"Michael Koblic" wrote in message
...

"Ed Huntress" wrote in message
...


[...]

I forgot one important thing: If you want to try epoxy, keep in mind that
its maximum strength, particularly in metal-to-metal bonding, is achieved
with a bond layer approximately 0.002" thick. Any thinner, and the
strength goes to pot -- especially peel/cleavage strength. I often leave
a little sanding grit in the joint to be sure I'm not starving it out.

It can tolerate a thicker layer, up to around 0.006" or so, without
losing a lot of strength.


Thank you and all the others.

I was not aware of copper being a problem with glues.

I have your "scratch-in" method saved in my works folder from last time
you mentioned it here and was going to try it next. The only reason I was
hesitating is that the reverse side of the brass foil is supposed to look
intact and in the past any speck of dust or other mechanical disturbance
produced blemishes which were impossible to get rid of. However, I guess
now is the time to try again, very carefully.

I'd try the Scotchbrite, on a flat piece of glass or something similar.


As for the optimum layer of glue I wonder if going to a coarser abrasive
would help by producing more pronounced peaks and valleys on both sides of
the material - perhaps just on the steel side.

It sounds like a reasonable idea. I've experimented a bit with grades of
sandpaper, however, and I prefer using finer grits. But you may be on to
something there.


I was going to try the solder paste method as a last resort. I have played
with a couple of different kinds and I don't like them for ordinary
soldering/silver soldering. However, this may be the right place for it.

--
Michael Koblic,
Campbell River, BC

Good luck. Let us know how it works out.

When you're bonding metal with strong adhesives, it's good to keep the
peel-strength/cleavage-strength issue in mind. That's one weakness of those
adhesives in metalwork. As an aside, this is what rivet-bonding is all about
in making aircraft wings. If you look at how the rivets are placed it's
clear that they're not being used for the sake of their shear strength, as
aircraft rivets normally are. They're there solely to keep the edges of the
wing skins from lifting and starting a peel failure.

--
Ed Huntress

"Ed Huntress" wrote in message
...


When you're bonding metal with strong adhesives, it's good to keep the
peel-strength/cleavage-strength issue in mind. That's one weakness of
those adhesives in metalwork. As an aside, this is what rivet-bonding is
all about in making aircraft wings. If you look at how the rivets are
placed it's clear that they're not being used for the sake of their shear
strength, as aircraft rivets normally are. They're there solely to keep
the edges of the wing skins from lifting and starting a peel failure.

--

Through trial and much error I found techniques of increasing a glue bond
strength that work for me (this is probably what proper engineers learn in
the first semester). Just changing the shape of the joint ever so slightly I
find the glue holds so much better (a cylinder glued to a flat vs. cylinder
recessed by a few thou *into* the flat - does not have to be a particularly
good fit, either. Also works for improving soft solder joint strengths. Then
there is less clean up then when using high temp soldering - but that is
another story!). Since I discovered the joys of press fit (now that I have
the machinery to produce one) things are even better. But there is no way
around it in this case and I shall have to defeat the pesky peel some other
way :-)

--
Michael Koblic,
Campbell River, BC

"Michael Koblic" wrote in message
...

"Ed Huntress" wrote in message
...


When you're bonding metal with strong adhesives, it's good to keep the
peel-strength/cleavage-strength issue in mind. That's one weakness of
those adhesives in metalwork. As an aside, this is what rivet-bonding is
all about in making aircraft wings. If you look at how the rivets are
placed it's clear that they're not being used for the sake of their shear
strength, as aircraft rivets normally are. They're there solely to keep
the edges of the wing skins from lifting and starting a peel failure.

--

Through trial and much error I found techniques of increasing a glue bond
strength that work for me (this is probably what proper engineers learn in
the first semester). Just changing the shape of the joint ever so slightly
I find the glue holds so much better (a cylinder glued to a flat vs.
cylinder recessed by a few thou *into* the flat - does not have to be a
particularly good fit, either. Also works for improving soft solder joint
strengths. Then there is less clean up then when using high temp
soldering - but that is another story!). Since I discovered the joys of
press fit (now that I have the machinery to produce one) things are even
better. But there is no way around it in this case and I shall have to
defeat the pesky peel some other way :-)

--
Michael Koblic,
Campbell River, BC

Yes, your cylinder example is a good one. In the first case there is a big
cleavage load. If you recess the flat to provide a shallow "socket" for the
cylinder, you have a shear load where they overlap, and that's where
adhesives are very strong.

A good example is the chassis of the Lotus Elise, which is also used in the
Tesla electric sports car. The chassis is made of tubular aluminum
extrusions that are bonded together with epoxy. The joints are
plug-and-socket types, or very close to plugs and sockets, in which almost
all of the load is in shear. Where there's no peel or cleavage,
metal-to-metal bonded joints can be stronger than the parent metal itself.

--
Ed Huntress