Re: Glass to metal adhesive

Richard.L.Klappal@att.com
Tue, 11 Apr 95 17:21:54 CDT

>> From best.com!owner-atm@ig2.att.att.com Tue Apr 11 17:06:05 1995
>> Date: Tue, 11 Apr 1995 14:18:58 +0700
>> From: rhill@LPL.Arizona.EDU (Rik Hill)
>> To: atm@best.com
>> Subject: Re: Glass to metal adhesive
>> X-Sun-Charset: US-ASCII
>> Sender: owner-atm@best.com
>> Reply-To: atm@best.com
>> Content-Length: 572
>>
>> >
>> > > Now for the risky part--attaching the mirror. As Steve Scampini
>> > >noted, acetic acid and Aluminum are not combatible.
>> >
>> > Perhaps a real chemist can confirm this, but I think you can immerse an
>> > aluminized mirror in undiluted acetic acid and nothing will happen.
>>In fact
>> > you can drown it in nitric acid and most other acids and nothing will
>>happen
>> > because alumimun becomes passivated by its ferociously strong oxide layer.
>>
>> I always attributed the good adhesive qualities to the acid etching
>> the materials being bonded. Am I wrong in this hypothesis?-Rik
>>
Its been more than 20 years since I was active as a chemist, but dredging up old memories, which may be risky:

Concentrated acids, especially those with organic chemical molecular components, have lower ionic concentrations than diluted acids, and there is some dilution where you end up with the maximum level of dissociation. That is, the highest concentration of acid ions (H+) and base ions (CH3COO-). More dilute spreads the ions out, less dilute forces them to recombine into a 'stable' compound (CH3COOH). This may contribute to reduced activity from the concentrated stuff, followed by reaction as you wash it off.

The same thing can occur with sulfuric, hydrochloric, nitric acids, but it also depends on what you mix it with. THESE THINGS CAN BE DANGEROUS OR DEADLY. THEY ARE CLASSIFIED AS HAZARDOUS MATERIALS. (Just in case any children are listening<g>).

Activities and reactivities leading to Aluminum acetate I just don't remember, but can try to find something in an old textbook.