On a much larger scale I once had the four platen lifting screws of a 60 ton hydraulic press rusted solidly into the bronze nuts that they screwed on. Nuts each had 4" of embedded thread. Machine had been in an intense fire, then dowsed with fire hoses, then left in a burnt out building for six years - they were solid.
I did much research on rust and its removal from threads! The best solution I found, and it eventually worked, was Citric Acid. I seem to remember that the volume of rust is something like ten times the volume of the original steel. Citric acid acts on the rust to form iron citrate, which is water soluble. The result is that over time the citrate migrates out into the body of the water allowing more acid in. This is unlike many other acids used for de-rusting which form insoluble compounds that although smaller in volume than the rust, are still larger than the original steel.
Now at this stage I'm NOT advocating citric acid for your micrometer, but I'd certainly use it in preference to electrolysis as you cannot be absolutely sure what metals you are dealing with.
.. the 60 ton press . . yes now working fine :)
I did much research on rust and its removal from threads! The best solution I found, and it eventually worked, was Citric Acid. I seem to remember that the volume of rust is something like ten times the volume of the original steel. Citric acid acts on the rust to form iron citrate, which is water soluble. The result is that over time the citrate migrates out into the body of the water allowing more acid in. This is unlike many other acids used for de-rusting which form insoluble compounds that although smaller in volume than the rust, are still larger than the original steel.
Now at this stage I'm NOT advocating citric acid for your micrometer, but I'd certainly use it in preference to electrolysis as you cannot be absolutely sure what metals you are dealing with.
.. the 60 ton press . . yes now working fine :)
Andrew Mawson, proud to be a member of MetalworkingFun Forum since Oct 2013.