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

[Cecil]

I don't think anyone was suggesting the use of zinc chromate on the chassis...

I only use it as a primer on the front panel and the knobs. 

I'm not a fan of any effort to try to duplicate the MFP coating...it was necessary in the jungles of SE Asia but not in my air conditioned shop/station.

I have one SP-600 that some mis-guided soul sprayed MFP all over the main tuning cap...it's slowly flaking off...drives the radio crazy.  The cap plates are gold plated to start with....didn't need any protection.

Cecil

Sent from my iPad

> On Oct 13, 2014, at 4:31 PM, Scott Overstreet <scott at becklawfirm.com> wrote:
> 
> 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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