Glueing optics to black anodized aluminum

[Fitzgerald]

We are having some difficulties gluing to black anodized aluminum; most
likely caused by the sealing process that closes the pores at the end of
the anodisation process.

I'm looking for hints/tips on what type of anodisation process and/or
glue to use:

- What type of acid do you use for anodizing? Standard sulfuric acid
anodizing (Type II)?
- What layer thickness do you specify?
- What kind of dyeing do you use? Organic dyes or electrolytically
deposited?
- What kind of sealing process do you specify? (hot deionized water?)

- What type of glue do you specify? (Epoxy / Silicon RTV?)
- Any particular recommendation for a brand / part no.?


Many thanks!

[Helpful person]

Why are you doing this? Is the part a mirror or lens? What's the geometry?

Normally one doesn't glue directly onto an anodized or painted surface.

http://www.richardfisher.com

[gghe...@gmail.com]

On Thursday, September 3, 2015 at 5:26:07 AM UTC-4, Fitzgerald wrote:

We stick diffraction gratings to anodized Al with Loctite 312,
the pack (from McMaster-Carr) comes with a primer and adhesive.
It's major use is to stick rear view mirrors onto car windshields.
It sets up pretty fast.. and if you are using gratings..
well be careful not to let it run into the grating grooves. :^)
The good news is it's only a very thin layer, so not a lot of
gunk in there to change the optical path length...
(I had issues with other glues either never quite curing, or changing
with humidity or temperature.)
Besides de-greasing the Al parts there's no other surface prep.
(well spraying on the primer..)

George H.

[Helpful person]

Sorry, outside my expertise. However, Loctite should be able to help. I assume that both parts are carefully cleaned before gluing and that the grating is not on a strange substrate.

http://www.richardfisher.com

[Helmut Wabnig]

Glass to Aluminium must leave room for temperature expansion.
Use small dots of glue.
Expansion coefficients differ a lot.

We used 2 component Araldite to glue mirrors on anodized Aluminium.


Elastic glue, silicone glue is not possible?


w.

[Helmut Wabnig]

On Thu, 3 Sep 2015 11:26:06 +0200, Fitzgerald
<john....@mailinator.com> wrote:

Glass to Aluminium must leave room for temperature expansion.
Use small dots of glue.
Expansion coefficients differ a lot.

We used 2 component Araldite to glue mirrors on anodized Aluminium.


Elastic glue, silicone glue is not possible?

================
Sorry, forgot something.
Any glue will shrink during hardening and possibly bend
the optical component.

w.

[Joe Gwinn]

In article <ms93k0$k6t$1...@dont-email.me>, Fitzgerald

Glass to anodized aluminum?

Beware differences in temperature coefficient - the glue cannot be too
hard. Some kinds of epoxy are soft enough, but most are too rigid.

Epoxy sticks to aluminum pretty well, if the aluminum is absolutely
clean. Anodize coating is porous and weak, so best to remove it.

Other than the above generic advice, will need to know what you are
doing and what problems you are encountering.

Joe Gwinn

[Phil Hobbs]

Commercial mounts are often Tufram or Polylube or the equivalent, i.e.
the pores in the anodizing are filled with fluoropolymer. That stuff is
pretty well impossible to glue to successfully, IME. If you're doing
your own, it might be easier, I don't know.

It's much better to remove the anodizing before sticking something down,
and do pay attention to the comments about CTE mismatch--hard epoxy is
strong enough to pull hunks of glass out of your mirror as the metal
heats up, as well as causing figure distortion.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net