Mailing List flyrotary@lancaironline.net Message #38135
From: M Roberts <montyr2157@alltel.net>
Subject: Amazing Transformation
Date: Thu, 28 Jun 2007 09:42:06 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Muriatic acid, (Hydrochloric acid) is available at builders supply stores. Used to etch concrete prior to painting. This is 2% Hydrochloric in water. Light yellow color. Stay out side for this one. Stay up wind. Wear rubber gloves and eye protection.
 
Use only plastic containers. Only store in the original container. Dissolves oxides of iron completely. Dissolves most nonferrous
metals. You will need to replace the rotor bearings. Works like magic.  Rinse with water and baking soda mixture.to neutralize
acid. Done over limestone gravel spills will dissolve into gravel and be neutralized. 
 
Lower (washed of oil and grease), rusted part into acid. Cover and let stand for several hours.  No rust will be left on the part.
 
Lynn E. Hanover 
 
Lynn,
 
I actually did know the hydrochloric acid trick.
 
Nasty stuff.
 
Actually the way I discovered the battery charger trick was a variation of the muratic acid trick. You take muratic acid and dilute it further. Like 2 cups for 5 gallons of water. It makes for a less hazardous solution to work with. Then you take a piece of wire and connect the rusty part to a scrap of aluminum. You put both in the weak acid bath. You now have a battery. The aluminum becomes the sacrificial anode and the rust is dissolved from the part.
 
The problem is acid does not remove carbon or grease so you have to get all of that off beforehand or it acts like a mask for etching.
 
The other problem is the acid will attack the base metal so you have to keep a close eye on it.
 
The really nice thing about the battery charger and washing soda trick is the washing soda is a detergent and a caustic which will remove grease. Also the solution is much nicer to work with.
 
You can leave it for as long as you like and none of the base metal will be removed.
 
Actually the two work really well in combination. You use the caustic bath to remove the rust etc. Then you hose off most of the black magnetite. Then you put it in the acid bath for a few minutes to get all of the magnetite out of the pits on the part. Then you hose it off again. Then you put it back in the caustic bath to neutralize the acid and passivate the metal.
 
Having used both methods, I like the washing soda for ease of use and lack of nasty byproducts.
 
Monty
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