[R-390] What is on the 390 chassis anyway

[Les Locklear]

Zinc Chromate primer was used on R-390 and R-390A series receivers front
panels and the knobs. Yeah, it is supposedly carcinogenic, but so is most
everything these days. I've used it on automotive battery posts to combat
corrosion among other things.

We've become so damn afraid of various chemicals and agents that as a
society I guess we ought to stay indoors and watch TV re-runs of All in the
Family or succumb...........

I still use certain banned chemicals as a degreasing agent. Oh, I forgot to
mention, I drink beer, Irish Whisky, wine in boxes too. I'm 71, blood
pressure is 120 over 70 and don't take any prescription medications either.

YMMV

Les Locklear

"The two most common elements in the universe are Hydrogen and stupidity".
Harlan Ellison
US science fiction author & screenwriter (1934 - )



-----Original Message----- 
From: Scott Overstreet
Sent: Monday, October 13, 2014 4:31 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] What is on the 390 chassis anyway

I don't know where all this zinc chromate stuff has come from. True,
zinc chromate paint has been used for years and years on aircraft
aluminum but I've never seen it on 390's.

The finish on 390 aluminum is "alodine" This is a very much still in
use, aluminum finish that , believe it or not, is available in quart
bottles in most automotive paint stores for a very affordable price----I
can't remember just what I paid for the last bottle I bought. There is
also "clear" alodine but this is not what you may want or was used on
the 390's.

Commercially, the process is a dip in caustic (lye) to clean and etch a
bit and then in a "bright dip" (?) to clean up the impurities left
behind (usually a bit gray) and then into the alodine tank. The
immersion period is usually about 45 seconds with fresh alodine and up
to several minutes for near dead  alodine. The longer in the tank, the
darker it gets which can be pretty dark brown. Ask Google for process
details.

Alodine on a rag can make things look better but things have to be very
clean for uniformity------wear rubber gloves, alodine stains.

Scott
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