[lum1n0l]

Currently studying passivation as well as acid cleaning of boiler systems
I understand that passivation involves the creation of a protective layer, but what I don't get is how hydrogen peroxide can fulfill that role. Specifically, how can it form said layer without corroding the metal piping itself, since it is a strong oxidant which accelerates rust?

[Hunter2]

The passivation with oxide is of course a corrosion. The thin layer will be created on the surface of the metallic material. H2O2 or HNO3 with Phosphate can do the job.

[lum1n0l]

does that mean that passivation is unreliable in the long term because it will eventually corrode all of the metal after repeated attempts?

[Borek]

does that mean that passivation is unreliable in the long term because it will eventually corrode all of the metal after repeated attempts?

Define "unreliable". Yes, nothing is eternal, but passivation still makes the lifetime of the system many times longer.