On Sun, 18 Jan 2015 11:53:05 -0600, "Paul K. Dickman"
wrote:


"Ed Huntress" wrote in message
.. .
On Sun, 18 Jan 2015 10:41:05 -0600, "Paul K. Dickman"
wrote:


"Ed Huntress" wrote in message
...
On Sun, 18 Jan 2015 09:13:14 -0600, "Paul K. Dickman"
wrote:


"John Doe" wrote in message
...
I do a lot with 6061 aluminum, without welding.

I'm expert at superglue. It's okay. Been trying Gorilla Glue. Even
with
the
surfaces sanded and clamped for 24 hours, seems it isn't even good as
superglue. Maybe I haven't given it enough effort?

What's the best glue for aluminum?

Thanks.

Lord 406/19 a two part acrylic.

a lot more expensive than super glue, but hands down the best thing I've
ever used for aluminum.

with intelligent joint design, you could assemble bookshelves with the
stuff.

Paul K. Dickman

I don't know that glue, but the properties look awfully good,
especially for use in a small shop without any equipment. It sounds
like it's formulated to give good peel strength, which is very
important in any metal-to-metal bonding.

I'd like to know how they get away with an aluminum prep that just
amounts to wiping with isoprpyl alcohol.

--
Ed Huntress

Not sure.
I was introduced to the stuff 10-12 years ago.
A photographer I know was having large (3'x4') prints mounted on 12g
aluminum sheets and creating a standoff and mounting system by gluing 3/4"
square extrusions to the back. The sign company that was doing the work
didn't want to do the fiddly bit so they told her what glue to use and she
gave it to me.

I called an engineer at the company and asked him what sort of prep I
needed
to do and he said "Don't worry about it. The stuff is specifically
designed
to work with dirty metal. As long as it ain't greasy or dusty, it'll stick
it together."

About a year later, I used the leftover glue (technically out of date) to
put together some frames out of 1 3/4" anodized angle for another client.
Simply cut them square, lapped one leg over the other and glued a short
piece of angle an the inside angle that didn't lap.

I was going to add rivets, but after I did a 2 ft sq. test piece, I
decided
the rivets would be a waste of time.

I still have the test piece. A decade later, you can still sit on it and
rock back and forth.

I have no problem recommending their products to anyone.

The adhesive does give off a strong sickly sweet smell when it is curing.
Have ventilation handy.

Paul K. Dickman

It must contain an etchant, or it creates its own conversion coating.
Otherwise, you're just gluing to a very weak layer of aluminum oxide.

I'll have to look into that one.

--
Ed Huntress

Here's a clip from a Dow paper on advancements in acrylic adhesives


The earlier "first generation" acrylics and the subsequent "second
generation" acrylics had certain
limitations, especially in metal bonding capability owing to limitations in
resistance to elevated
temperature exposure and subsequent resistance to harsh or corrosive
environments. As reviewed by
Damico (1990), the primary improvements in adhesives based on MMA monomer in
the 1980's
involved improvements in the ability of these products to bond as-received
metals, especially
aluminum steel and stainless steel, with little or no surface preparation.
The primary enabling factor
was the incorporation of phosphoric acid derivatives of methacrylate
monomers that chemically
interact with metal oxide surfaces to strengthen the normally weak
interfacial layer between the
adhesive and the base metal and to protect it from corrosive attack in harsh
environmental conditions
(Zalucha et al. 1980)

http://msdssearch.dow.com/PublishedL...romPage=GetDoc

Paul K. Dickman

AHA! So it's built-in conversion coating chemistry. Phosphoric-acid
anodizing (PAA) is the conversion coating they have used on aluminum
for adhesive bonding, for the past 50 years or so. That's what they
always used on epoxy-bonded aircraft structures and skins. Maybe they
still do.

Thanks, Paul. That's really good stuff to know if you bond metal
together with adhesives.

--
Ed Huntress