Those "silver" versions of various Pietta revolvers - do they also have a protective finish, albeit of a different kind, or they lack that sort of protection?
I asked an engineer who said that there's no real way to know for sure if polished steel has undergone a "passivation" process or not.
It's often performed to satisfy the requirements of government specifications that require that everything possible is to be done
by governement contractors to prevent rust or corrosion of parts being made for the military, or for the medical field.
It's invisible to the naked eye.
However it is often performed on steel that has undergone "electro-polishing" whether it's stainless steel or not.
If it were done, the thickness of the protection would be on the sub-micron level.
Perhaps Valentina knows?
From Google:
Passivation is the process of treating or coating a metal in order to reduce the chemical reactivity of its surface.
In stainless steel,
passivation means removing the free iron from the surface of the metal using an acid solution to prevent rust.
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What is the passivation process?
Chemical
passivation is a two step
process.
The first step is to remove any free iron or iron compound that is on the surface, otherwise this iron will create a localized site where corrosion can continue.
Acid is used to dissolve away the iron and its compounds.
The surface itself is not affected by this
process.