If you don't mind mechanically altering your sample, you could sand,
grind, or shot blast it to get a majority of the scale off and try to
get back to base metal. My impression is that you don't want to do
this and are looking for chemical means to reverse oxidation.
I'm not sure but a furnace treatment in a reducing atmosphere at high
temperture would make the oxide unstable. You want to reduce the
oxygen partial pressure around the treated sample and drive the metal
oxide to become a metal again. I don't know the rate of this reaction
or which atmosphere would be best but I hope that's a start.
There may also be strong etches you could use. For example 10% nitric
acid (depending on yoru alloy) and after scratching the exisiting oxide
you might be able to eat out the steel underneath to remove the oxide.
There are probably better chemical polishes out there though.
These are my guesses.
it seem like blue brittleness. this usaully occure when steel fractures
above 450 C. a blue color film forms on the fracture surface. if it is
not that than it will be simply scale which u can remove by acid
pickling. H2so4 and one other acid is used for this purpose search web
for the exact composition and temperature of the solution. this process
is common in cold rolling mills where hot rolled steel is to be cold
ibtesam hasan abidi
Asst: eng: manager OPL
Metallurgy and materials engineer
NACE certified cp technician