[R-390] Alodine and hexavalent chromium

[John KA1XC]

Oh OK, yeah the chemical stripping only takes care of  the surface,
scratches and pitting need sanding or grinding to clean up.
Out of curiosity how much is the plater charging for how many parts? Might
need to go this route someday.

The rear panel work that I did was a couple of years ago and the radio isn't
in front of me now so I can't take a peek, but as I recall the damage was
only in one area on one side (I think the inside) , where some kind of
corrosive gook had seriously damaged and discolored an area.

The lettering in the back was in good condition and I didn't want to mess
with it or take on a re-lettering job so basically what I did was mask it,
or possibly even masked the entire back side with ordinary masking tape
which worked very well while I did the metal prep and Alodining. Anything
that can keep the surface dry for several minutes will work as a mask, and
for masking small areas wax or crayons would probably work well.

(Arggg, did you ever have hot and sour soup go down the wrong pipe?, you
should have seen what just happened the monitor!)
=:^0
John


> The reason I wanted to wet-sand the pieces is they weren't in really great
shape.  Scratches, small oxidized patches, etc., made me want to get them in
physically better condition before any surface finishes.
>
> The center shelf seemed to have a rough texture about it that I wasn't
sure would come out if just chemically stripped.  I got a lot of the old
finish off and it went down the sink.  I assume there wasn't enough of
anything in that to be a hazard.  As someone else mentioned, once it has
dried and done its thing, it isn't as hazardous as when in liquid form.
>
> As I said, the local place is quite reasonable and I'd rather someone do
it right than have me messing it up on top of creating a potential
biohazard.  There's a lot of things I can do, but some things I'd just
rather leave to the pros.
>
> You mention you did a back panel.  Did the process destroy the lettering?
I assume it did.  What did you (if anything) about that?
>
> Thanks to all for the kind responses and advice.
>
> Barry(III) - N4BUQ
>
> >After Alodine is applied and dried I believe it's totally safe (as long
as
> >you don't eat it). It is commonly used as a surface finish on all kinds
of
> >aluminum parts or as a surface prep for painted aluminum to increase
paint
> >adhesion, like on the R-39x dial bezel. It is a very, very thin coating,
> >usually 0.5 to 3 thousands of an inch, and is easily removed by sanding
or
> >by phosphoric acid metal prep solution or a lye bath as Hank suggested.
> >
> >If you are sending your pieces to an Alodiner are you sure you need to
> >remove what's already there?; they will probably throw the parts in an
acid
> >bath first thing.
> >
> >It IS something you can do at home, but aside from the cost of buying a
> >gallon and having it shipped, you need to practice a bit to get the
coating
> >to be uniform and the correct thickness to match the other parts. (longer
> >soak or brushing = heavier coat = darker color). If you screw up the part
> >you can always throw it back in the lye bath and start over :^) I've done
> >the R-390 IF coil cans, dial bezels, and a back panel with good results,
but
> >it's not something I'd want to do frequently.
> >
> >For *small* quantities of the stuff that are used for home projects I
> >wouldn't worry about disposal issues, but please don't throw the used
stuff
> >on the ground. You definitely want to wear gloves to protect your skin
(and
> >to keep hand oils off the prepped part), and it can permanently stain
> >anything it touches.
> >
> >John
> >
> >----- Original Message ----- 
> >From: <N4BUQ at aol.com>
> >To: <R-390 at mailman.qth.net>
> >Sent: Thursday, January 13, 2005 11:48 AM
> >Subject: [R-390] Alodine and hexavalent chromium
> >
> >
> >> I've been doing a bit more looking into getting the panels for my
R390A's
> >re-alodined. Turns out this stuff is hazardous as it contains hexavalent
> >chromium (chrome?). Around here, you have to dispose of this stuff
properly
> >so I might not be trying this at home after all. Fortunately I've found a
> >place that will do the lot of parts for a reasonable price.
> >>
> >> This got me to wondering how hazardous it is to remove this coating. Is
> >it safe to wet-sand the parts to remove the old coating? Is the amount of
> >coating removed so small that it is insignificant?
> >>
> >> Just wondering...
> >>
> >> Barry - N4BUQ
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