Hello Bill/All,
I have a lot of long term experience with some of the products mentioned
which may be of use to you. Here at FX, we have been using several
solutions to the problem of gluing dissimiliar materials together for
exposure out of doors.
We originally came up with the British Petroleum world image program in the
mid-eighties, and we manufactured modular convenience stores, canopies, and
car washes for them until 1994 or so (we actually built and shipped two
stations to the UK as well...one in a place near london called Rushett, and
one in Milton Keynes). I still visit some of the stations we did locally,
and I can attest to the following:
We use the closed cell foam double-stick tape, and it works great but
does degrade over time. Heat exposure and repeated flexing (due to
different rates of expansion between materials) eventually breaks down the
cells in the foam between the adhesive layers. UV is not kind as well, if
the light can reach the tape, turning it yellow and brittle.
Standard silicone is good, but is affected by UV as well, and the clear
variety can actually transmit light back into the interior of a joint. It
will eventually turn yellow and break down...I learned that little lesson on
top of a canopy in Florida, and that is one of the reasons why gas station
canopies leak on your head when you are pumping gas.
Epoxy in most cases is brittle due to it's hardness, although there are
slightly more flexible varieties. It is best used in situations where the
materials are similiar, and there is not much expansion/contraction
anticipated.
My favorite adhesive to use for joining different materials in hostile
environments is Dow Corning Silicon adhesive #795. It is wonderful stuff,
and will join just about anything provided the surfaces are clean when you
start. It is available in many colours, but I use black because UV is
absorbed at the surface and is not transmitted into the interior of the
material. This material was originally formulated as a sealant for
architectural glazing applications where the mullion (usually anodized
aluminum) comes in contact with the glass panes and extends over long linear
distances. The silver panels we used to clad the BP stations (Aluminum
composite material, or ACM) can expand as much as .25" in 8 feet of
material. We designed special joints to compensate for this and prevent oil
canning of the panels, but where we had to bond these panels to steel
structure or aluminum mullions we used 795. They still look good and are
holding well in the hostile environment of a petroleum station...even out at
the pump line.
The material takes a little while to grab though, just like regular
silicone, so hold the parts together with some tape until the material
grabs. Full cure takes about 24 hours. If you decide to use this material,
contact me off list and I'll tell you more details about how to use it, tool
joints, etc.
I hope that this helps, and I'd love to see a pic when your job is done.
Jim Tallman
Sr. Designer
FX Studios
513.829.1888
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, August 29, 2001 1:23 AM
Subject: Gluing Stainless to Aluminum
> I am consulting on a local sun sculpture which requires that an aluminum
> backing be glued to 6" x 24" stainless steel mirrors. They can't be
screwed
> on for fear that the screws and holes might distort the mirror, and hence
the
> image. The temperature exposure will range from -20 to 120 degrees
> Fahrenheit seasonally, and I think that the glue must be able to forgive
the
> small difference in the metals' coefficients of expansion.
>
> Any recommendations? Silicon glue, polyurethane, epoxy, or something
else?
> Thanks-
> Bill Gottesman
>
