[sdiy] Panel Finish

Wed Apr 1 20:15:34 CEST 2009

Scott,

I will be applying an acrylic clear-coat to protect the decals more than the
aluminum, although it will prevent scratching.  My can of clear-coat says it
works well on aluminum, as long as the surface is clean when you start.  I
won't be peeling the protective backing off of my sheet until I'm ready to
actually stick the decals on, and then clear-coating immediately to avoid
dust, fingerprints, etc.  (At least, that's my best-laid plan...)

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C. V6T 1Z4
Canada

Tel 1-604-822-3679
Fax 1-604-822-3619

"PERFECTA FINGAMUS SERVIAT NATURA"

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> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of Scott
> Sent: Wednesday, April 01, 2009 10:15 AM
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Panel Finish
> 
> Well, it was that thin oxide coating I was referring to.  My panels are
> still relatively bright, even after a year or 2 of being bare.  I thought
> aluminum oxidized to a dull gray.  That still wouldn't' be all bad, but
> the shiny brushed look they've got now is better.
> And as others have mentioned, I have read that nothing sticks to the
> oxidized aluminum, and envision a cracking, peeling finish in 10 years
> time..  I have no idea, though, how finishes will really hold up.
> 
> -----Original Message-----
> From: David G. Dixon [mailto:dixon at interchange.ubc.ca]
> Sent: Wednesday, April 01, 2009 11:36 AM
> To: Scott; synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Panel Finish
> 
> Hello, Scott.
> 
> Here is the good news: Aluminum doesn't oxidize!
> 
> As you may know, aluminum is characterized as a "reactive" metal because
> it
> is so far down on the electrochemical series.  If ground to a fine powder
> and mixed with iron oxide, it will actually catch fire (these are the
> simple
> ingredients of the famous "thermite" bomb).  However, aluminum has one
> all-important redeeming feature which allows us to forget all that in
> everyday use: It forms a very coherent passive layer in the presence of
> oxygen.
> 
> Yes, aluminum does oxidize; very rapidly, in fact, according to the
> following reaction:
> 
> 2 Al(metal) + 3/2 O2(g) ==> Al2O3(s)
> 
> However, this reaction only proceeds to the extent that a mono-molecular
> layer of aluminum oxide forms on the surface.  This oxide layer is so thin
> that it is totally transparent, and the aluminum surface looks perfectly
> pristine.  The only problem with aluminum is that it has absolutely no
> resistance to acid attack.  In acid, because aluminum is so far down the
> electrochemical series (far lower than hydrogen gas), the following
> reactions will occur.  First, the oxide layer is dissolved away:
> 
> Al2O3(s) + 6 HX(aq) ==> 2 AlX3(aq) + 3 H2O(l)
> 
> Where X is any common acid anion (chloride, nitrate, sulfate, etc).  This
> leaves the bare aluminum underneath unprotected, and it can then react
> electrochemically with the acid (i.e., corrode) to form hydrogen gas:
> 
> 2 Al(metal) + 6 HX(aq) ==> 2 AlX3(aq) + 3 H2(g)
> 
> You may have noticed that aluminum foil will develop holes if used to
> cover
> acidic food like spaghetti sauce.  This tells you how un-resistant to acid
> it is.
> 
> Indeed, some researchers (including two professors in my department) are
> looking at aluminum as a virtual "gas tank" for hydrogen-powered cars.  Of
> course, this is a totally stupid idea (sh!) because the manufacture of
> metallic aluminum (by molten salt electrolysis from anhydrous alumina in
> the
> famous "Hall-Heroult" cell) is one of the most energy-intensive and
> environmentally unfriendly processes around (and is also, unfortunately,
> the
> only industrially viable way to make aluminum).  Not only is the process
> very inefficient with respect to electricity usage, but it also converts
> vast quantities of carbon to carbon dioxide through the consumption of
> huge
> graphite electrodes.  Hydrogen generated in this way would cost much more
> energy to produce than that generated by simple electrohydrolysis or fuel
> cells, which can run off of fuel made from agricultural waste.  Also, in
> order to use aluminum in this way, one would have to carry around not only
> huge chunks of aluminum in ones car, but also large quantities of
> concentrated acid solution to dissolve it in (I'd really hate to be the
> cop
> at the scene of THAT accident!) and all of the associated
> corrosion-resistant (read: expensive) equipment with which to pump it
> around.  Oy!
> 
> I am in the process of making Al synth module panels pretty much exactly
> like you are: bare aluminum with DecalPRO dry transfer decals affixed
> (www.pulsarprofx.com) and covered with acrylic clear-coat to protect it.
> It
> should last indefinitely!  Just keep acid away from the bare aluminum!
> 
> Cheers,
> Dave
> 
> David G. Dixon
> Professor
> Department of Materials Engineering
> University of British Columbia
> 309-6350 Stores Road
> Vancouver, B.C. V6T 1Z4
> Canada
> 
> Tel 1-604-822-3679
> Fax 1-604-822-3619
> 
> "PERFECTA FINGAMUS SERVIAT NATURA"
> 
> The information in this email and in any attachments is confidential and
> intended solely for the attention and use of the named addressee(s).  It
> must not be disclosed to any person without the writer's authority.  If
> you
> are not the intended recipient, or a person responsible for delivering it
> to
> the intended recipient, you are not authorized to and must not disclose,
> copy, distribute, or retain this message or any part of it.
> 
> > -----Original Message-----
> > From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> > bounces at dropmix.xs4all.nl] On Behalf Of Scott
> > Sent: Wednesday, April 01, 2009 7:56 AM
> > To: synth-diy at dropmix.xs4all.nl
> > Subject: [sdiy] Panel Finish
> >
> > Is there any long term problem w/ spraying bare aluminum w/ lacquer or
> > poly?  I've been making panels by transferring an image  to the bare
> > (silver) aluminum, then coating.   Will the aluminum still oxidize under
> > the finish and cause trouble 10 or 20 years down the road?
> >
> > thanks!   - still trying to work out the best diy method for panels!  (I
> > used to (about 10 years ago now) use some translucent paper, glued on,
> > then sprayed w/ poly.  That looked great until a few years later when
> the
> > paper started absorbing moisture and expanding/wrinkling!  So far this
> > toner transfer is working well)  Unfortunately I like black graphics on
> > the bare metal.  I've found several people have posted great
> explanations
> > for their methods of making professional looking black panels w/ white
> > text, but not black text on silver.  The toner transfer does look good,
> > but I have concerns about the longevity.
> >
> > thanks again
> >
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> 
> 
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