[R-390] Alodine and hexavalent chromium

John KA1XC tetrode at comcast.net
Thu Jan 13 17:25:05 EST 2005 

That's not bad at all considering the messy work that it saves.
Keep in mind that if your Alodining and masking adjacent areas then there
*will* be a visible difference in the color of the new coating as compared
to the original under the mask. If the masking around the lettering is done
very neatly then it might even give it a "label" effect which might be
interesting.

As Jay pointed out a couple of posts back there is no standard for color
matching between batches. Heck even within the same batch and on the same
part I've seen color differences.

John


> I may try masking.  If I can work with the guy at the plater, then it
would be worth it.
>
> He said it would be about $40 to for 8 parts.  Sounded like it wasn't set
in stone and a few back panels wouldn't run it up much past $50.  Worth it
to me to have these looking good again.
>
> Be sure to wash down that hot-n-sour soup with a little wasabe. :P
>
> Barry(III) - N4BUQ
>
>
> >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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> >> >
> >> >
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