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.
On Wed, 7 Jul 2010 23:03:04 -0700, "Michael Koblic" wrote the following:
Could it be the difference in the coefficient of expansion between the brass and steel?
Give it one more try, this time using 3M Super 77 spray adhesive. It's the only one I can use (on my laptop glare guards) which will go on evenly and finely.
Or, if it doesn't have to be electrically connected, you might try a thin double-sided adhesive tape. That might give them enough separation if the COE is high up there in the GWN.
-- It's also helpful to realize that this very body that we have, that's sitting right here right now, with its aches and its pleasures, is exactly what we need to be fully human, fully awake, fully alive. -- Pema Chodron
Brass does not play well with epoxies. If I recall correctly it is the copper that causes the problem. You can buy epoxy that is especially formulated to work with copper at your big box store. It is sold to glue copper pipe so look for it in the plumbing section. About two or three times as expensive as ordinary epoxy.
It won't kill you . Right away ... actually , the good stuff (Formica 140 ...) will give you a pretty good buzz , with a lingering headache afterwards . The non-flam stuff stinks so bad you won't want to breath the fumes , and the latex/water based variety has basically no odor . Try 3M weatherstrip adhesive , spread like contact and the brass applied while it's still tacky .
And that STILL doesn't work, in my experience. I was trying to avoid a big solder job when installing a replacement shower valve, involved about a dozen joints. Ended up with a shower in the wall instead, most leaked. So ended up with a solder job anyway. And a nasty job trying to get the stuff apart again after gluing.
Any reason the O.P. can't sweat-solder the brass to the steel? You can get solder-in-flux paste that works well for that. If the stress at the joint is in shear or peel, that may be the only way. Would have been my first choice.
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.
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.
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.
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.
I'd try the Scotchbrite, on a flat piece of glass or something similar.
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.
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.
I didn't think that a very tenacious adhesive. I use #77 to adhere abrasive paper to glass when I want to do some scary sharpening. If I don't leave the paper on for too long I can pull it up rather easily. If I go say, 6 months, well, it really stick but by then humidity changes has caused the abrasive paper to hump up in places making the paper useless.
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 :-)
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.
3M make a thin double sided tape , that just about is indestructable ,I cant recall what its called ,but they use it for hanging the BP logo signs on the gas stations here. (Should I have mentioned BP here to you Americans)I apologise for that , but it's the only thing that I could think of at this time. The other option is one of the adhesives they use in the car repair industry , one that comes to mind is the one they use for gluing the door skins onto the frames .Sikaflex is one brand name that springs to mind.
Then I been doin' it wrong for over 35 years ! Laminated somewhere in the tens of thousands of square feet of P-Lam with hundreds of gallons of the stuff over the years , an' I ain't dead yet . Lost some small bits and pieces of fingers (to router bits ...) over the years , does that count ?
On Thu, 08 Jul 2010 22:31:18 -0400, Wes wrote the following:
It's exceedingly more tenacious for porous materials, Wes. But if you don't ike that, try 3M #90 Hi-strength.
for too long
For ScarySharping, spray it on MDF and stick the paper to that. I use whatever flat surface is handy at the moment, including laminate countertops. The 50% of the times I do it dry, it doesn't matter.
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