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

[Barry]

Several years ago, I found a company here in town that would still do the conversion for me (not sure it was Alodine but it was very similar).  Was rather expensive to have that done since it was in such a small quantity.  Not sure if they'll still do that anymore.

Yes, I think you can still get Alodine; however, I think you have to be careful about disposal of the rinse water, etc.  I think it's classified as a heavy metal (not a chemist so not sure of that nomenclature) and I think you can get into some serious trouble if it is not disposed of properly (letting it go down the drain, etc.).

I believe zinc chromate was indeed used on the R390/R390A.  It was the primer on the front panel (and possibly the knobs).  It is VERY difficult to remove.

Regards,
Barry - N4BUQ

----- Original Message -----
> From: "Scott Overstreet" <scott at becklawfirm.com>
> To: r-390 at mailman.qth.net
> Sent: Monday, October 13, 2014 4:31:18 PM
> 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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