Summary for dissolving steel and not aluminum Discussion
Dissolving steel and not aluminum is the goal in this thread, where Chris Osgood asks for a fast chemical method to remove carbon-steel laminations from an AC motor squirrel rotor while leaving the aluminum cage intact for porosity inspection. Jeffrey Holmes, CEF, replies that the steel can be removed by a reverse sulfuric acid strip process: the steel is electrochemically dissolved while the aluminum is oxidized, effectively anodizing it. Chris confirms that he wants to keep the aluminum and dissolve the steel, and says he will try 15% sulfuric acid with reverse current. Guillermo Marrufo then asks about bath temperature, noting that anodizing temperatures matter to avoid aluminum attack. A follow-up answer says some aluminum will dissolve, but below 70 °F the loss should be negligible. The thread therefore points to reverse sulfuric acid stripping as the practical approach, with cool bath temperature helping protect the aluminum.
Q. 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
2005
 | A. Reverse current in 15% sulfuric acid should do the trick.
2005 A. I think the inquirer wants 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).
2005 |
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, New York USA
2005
Q. 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
2005
A. Some aluminum will be dissolved, but at temperatures below 70 °F the amount will be negligible.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
2005
A. 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
December 14, 2011
Q. How can I dissolve low carbon steel?
El Tavasoli
– Montreal, Canada
October 23, 2017
Hi El. Under the circumstances I can’t understand what your question is. Please introduce yourself and your situation and explain your objection to the answers already provided. Thanks and good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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October 2017