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Re: Follow Up: Re: how to remove rust from inside old gas tank

To: "Marc" <smarc@smarc.net>, "shop-talk Talk"
Subject: Re: Follow Up: Re: how to remove rust from inside old gas tank
From: "Kai M. Radicke" <kradicke@wishboneclassics.com>
Date: Thu, 24 May 2007 14:34:04 -0400
Marc wrote:

> Then I purchased a gallon of Evapo-Rust, dumped it in the tank, and left 
> it to sit over night. Checked it this morning, and was rather surprised to 
> find it ACTUALLY WORKS AS ADVERTISED! You coulda knocked me
> over with a feather!

EvapoRust does work (and for someone else who asked, this is the stuff Moss 
Motors sells on their website if that helps you find it).  However, it is 
expensive and the effectiveness of the solution seems quite short - at least 
with my expectations on how much it costs per gallon.

Randall later wrote:

> I suspect good ol' phosphoric acid works just as well or better.

It does.  This is what my machine shop uses to clean heavily rusted blocks 
before putting it in their other cleaning aparatus (jet spray, oven, airless 
shot blast is the usual procedure).  What do they use?  I asked once and 
they told they mix it up themselves, using regular Molasses.  The key was to 
let the solution sit for some period of time before using it, to allow it to 
ferment.  It seems fermenting Molasses produces phosphoric acid.  The mix 
ratio they used was something like 7:1 water to molasses.

I suspect that any acid solution will bring worries of hydrogen 
embrittlement of the base metal.  Although this could be the reason that 
they then bake the blocks after being rinsed in the jet spray cabinet.

What else?  They kept the plastic drum outside because the mix STUNK!  Which 
is one of the things that has kept me from mixing up my own molasses rust 
remover.

Kai 




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