A much diluted batch of muriatic acid eches alum really well,followed by
rinse in water. Also works really well for cleaning silver plated
parts,ceramic tubes,etc...Dip in/out fast depending on dilution ratio,full
strenght might eat the part..Vinegar cleans alum super well as does glass
cleaner..I have cleaned a few yc-156`s in muriatic acid full strength and
they look like new...Takes a few seconds followed by flushing with clean
water and blow dry..Got wind?73,Jim..
----- Original Message -----
From: "Larry" <larry@w7iuv.com>
Cc: "'Amplifier- List'" <amps@contesting.com>
Sent: Tuesday, April 24, 2007 10:18 AM
Subject: Re: [Amps] Surface Cleaning Tarnished Aluminum
> Robert Bonner wrote:
> > I thought we covered this last week. You don't want to use LYE on
aluminum
> > unless you want it to GO AWAY. It dissolves it, acid works more
controlled.
> > Lye would cause more pits.
> >
> I gotta jump in here.
>
> Lye, if used with a bit of intelligence, does not "dissolve" aluminum.
> At least not any more then you would want to in the first place. I use
> the stuff all the time on aluminum and it works great for putting a nice
> matte finish on parts and is a reasonable surface prep prior to painting
> if you don't have the resources to do a professional prep.
>
> As far as the air variable cap surfaces, all the Johnson and Caldwell
> caps I have seen appear to have had the plates tumbled. Depending on the
> tumbling media used, the surface can be nicely de-burred down to the
> microscopic level and leave anything from a matte to a polished finish.
> Although I have the resources to tumble small parts, I don't have to
> patience to do it. A proper job may take several days depending on the
> media used and the type of "polish" desired.
>
> If I were to re-build a air variable with the resources I have here, I
> would dis-assemble it and using 400 grit wet-or-dry paper carefully take
> off the high spots. Then I would do a light etch with lye (sodium
> hydroxide). The lye will etch away all the microscopic ridges left by
> the sandpaper and leave you with a nice matte finish that will look good
> under the microscope. Any "potholes" that might be left on the plates
> won't matter as long as there are no high spots or sharp shapes or edges.
>
> As has been said here recently, never dump parts in lye that have blind
> holes tapped into them. I have not had any problem with drilled and/or
> tapped holes in sheets or plates, but have had a bit of trouble with
> blind holes. Of course, I use a lye concentration suitable for the job
> at hand and watch it all the time it's in the bucket.
>
> The acid wash has always been a problem for me as the acid I would like
> to use is much more difficult to obtain then sodium hydroxide. Has
> anyone used white vinegar for this?
>
> 73, Larry
>
> --
> Larry - W7IUV
> DN07dg
> http://w7iuv.com
>
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