"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