Metallic magnesium without an oxide layer does not exist even in vacuum because MgO forms on metal surface at extremely low O2 partial pressures. Oxide free magnesium can only be obtained by evaporation in closed ampule (http://www.periodictable.ru/012Mg/Mg_en.html). So, removing MgO from the substrate will not work because new MgO layer is formed immediately.

Otherwise, theoretically, it would be possible. For example, to evaporate Mg without destroying of MgO, but the MgO layer without substrate will be in powder form.

Dear Dr. Verlotski, thank you for taking time to answer my question in such a detailed manner. Because of the nature of my MgO-based coating, which is almost 20 micro meters thick, I think it would be possible for the coating to remain intact if I manage to dissolve away the substrate. however, I'm looking for a chemical method rather than a physical one, such as evaporating, which will inevitably induce a thermal stress in the coating and damage it.

On the other hand, Since one of the main reasons that I intend to do this is to closely study the interface between the coating and the substrate, I might be able to tolerate a nano meter- thick MgO oxide layer formed after i dissolve the original thick coating, in case that it somewhat reproduces the substrate topography.

Thanks again for your response - Parsa

If there is only a detachment of 20 μm thick MgO layer in order to investigate the topography of the substrate, there are several possibilities:

1. Boil in warm water (MgO layer becomes loose and falls off),

2. High pressure cleaning with water (water steel destroys the brittle MgO layer),

3. Sandblasting with solid CO2 (gentle sandblasting method),

4. Several thermocycles in liquid nitrogen (layer decreases due to differences in thermal expansion coefficients),

5. Impregnating the layer with polymer resin and then thermocycling into liquid nitrogen (layer sticks to and falls with the polymer),

6. Ion purification (bombardment with argon ions) into a PVD system,

...

Thanks for your great response Dr. Verlotski, I'm going to try your first suggestion soon and I'm really looking forward to see if it will work, hoping that the problem can be solved this easily. However, considering the fact that the bond between the MgO coating and the Mg substrate is a very strong chemical bond, I'm not optimistic about it. If that didn't work out, I'm going to try your other suggestions afterwards as well. I'd really appreciate it if you'd share any other possible ways that might come to your mind.

Thank you so much for your kind answers again - Parsa