I've used this caustice soda (sodium hydroxide) treatment on aluminum many
times, especially for front panels, with good luck.
Aside from the somewhat dangerous aspects of this prceedure, a real problem
is that if you are going to drill and tap any of the treated parts, do so
after the treatment.
If you drill and tap, and then treat the aluminum, the sodium hydroxide will
considerably enlarge the holes, and reduce the threads, to the point that
the bolts will easily strip them out.
As I often say: "Been there, done that".
73, Barrie, W7ALW
----- Original Message -----
From: "Peter Chadwick" <g3rzp@g3rzp.wanadoo.co.uk>
To: "Steve Flood" <flood@ixi.net>; <amps@contesting.com>
Sent: Tuesday, April 10, 2007 7:33 AM
Subject: Re: [Amps] amp hardware
> Steve asked:
> >If I'm building up an amp (the RF compartment particularly) with aluminum
sheet and angle stock, should I be using aluminum bolts/nuts/washers to
avoid galvanic corrosion?<
> Is it going to be in the shack, or outside in a damp shed?
> If in an indoor shack, I wouldn't bother.
> Even in a damp shed, I've had no problems with aluminium and BZP (bright
zinc plated) steel hardware. For parts in a RF field, I'd use plated brass
for preference. . I've never found aluminium alloy screws too succesful,
although it may be that I'm too heavy handed - they always break before they
seem to be tight!
> It's worthwhile for a nice finish to 'soak' the aluminium for 15 minutes
or so in a strongish caustic soda bath. Do it in a well ventilated area
because of the hydrogen given off. Afterwards, ideally dip in a 20% nitric
acid bath, and if that isn't available, swab down with a cloth soaked in
vinegar - this will remove the black deposit. It helps paint to stick, too.
An alternative attractive finish is a wire brush in the electric drill. In
that case, wear goggles and gloves, and afterwards, give it a coat of clear
lacquer. Even if the aluminium isn't in view, it's good workmanship.....
> 73
> Peter G3RZP
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