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Dissolving Steel and NOT Aluminum

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I am looking for a chemical that will dissolve carbon steel and not aluminum (a100 or a380). Basically I have a squirrel rotor from an ac induction motor and I'm looking to dissolve the steel laminations and leave the aluminum cage so I can inspect for porosity etc. Is there a magic chemical? Also, I would like for this chemical to do this rather quickly...not weeks but days, if possible.

Thank you!

Chris Osgood
OEM - Rochester, NY USA


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Strong oxidizing acids like nitric acid theoretically dissolve steel while not dissolving aluminum. I don't know if this will prove safe and practical; bench tests will be needed first.

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


First of two simultaneous responses -- +++++

Reverse current in 15% sulfuric acid should do the trick.

jeffrey holmes Jeffrey Holmes, CEF
- Spartanburg, South Carolina



Second of two simultaneous responses -- +++++

Turning Ted's response back around, as I think the inquirer wanted to dissolve steel and retain the aluminum, this can be done using REVERSE SULFURIC ACID STRIP. Basically the steel is electrochemically dissolved while the aluminum is oxidized forming aluminum oxide (a.k.a. anodizing the aluminum component).

Milt Stevenson, Jr.
Anoplate Corp

Syracuse, New York



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Thanks guys.

Correct, I am looking to keep the Al and dissolve the steel. I'll try the 15% sulfuric with the reverse current.

Chris Osgood
- Rochester, NY USA


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My answer was not very good. I'm glad you got better advice!

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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Gentlemen,
Anodizing is certainly not my field but I didn't notice any reference to the temperature of the acid in the previous advises. I understand the temperature for anodizing must be quite low to avoid attack to the aluminum. Is this correct or is it applicable in the case of this gentleman from Rochester?

Thanks,

Guillermo Marrufo
Monterrey, NL, Mexico


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Some aluminum will be dissolved, but at temperatures below 70F the amount will be negligable.

Jeffrey Holmes, CEF
- Spartanburg, South Carolina

December 14, 2011

Here's another possible solution: Boil the part in alum. I do band instrument repair, and a common problem we encounter in this trade are steel screws or rods seized inside brass parts. One way to remove the steel is to boil the part in a solution of alum and water. This will rapidly rust the steel and it corrodes away to nothing. It has no effect on brass, copper, nickel, silver or gold. I don't know if alum has any effect on aluminum, I did not find any information on that in the 60 seconds I searched google before writing this post. If you try this method, be sure to add water to the solution every hour, as it will boil off rapidly.

Matt Scott
- Wilmington, North Carolina, USA

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