Oxidation

A common concern regarding the feasibility of gem based APM is that nanoscale parts will oxidize.
(See: Common critique towards diamondoid atomically precise manufacturing and technology)
This is a non-issue though as the (surface facing) target materials are
either oxidation resistant or already fully oxidized.
See: Gemstone-like compound

Pure metals and metallic alloys are not a focus exactly because of their oxidation tendency.
And a few other reasons like diffusion and mechanical inferiority.
See: Pure metals and metallic alloys
Metals still can be mechanosynthesized under certain constraints like

• low temperature and/or
• constrained atom placement freedom

Advanced systems will be able to perfectly seal and safe-keep their internals form oxidation.
To give a weak analogy: Juts like an apples or bananas do not get brown inside so long they're not cut open.

Fruit interior analogy

See main page: Fruit interior analogy

Related

• Fruit interior analogy
• Pure metals and metallic alloys
• Chemical stability
• Passivation (disambiguation)
• Nanoscale surface passivation (old: Surface passivation)
• Macroscale surface passivation
• Passivation layer mineral
• Common critique towards diamondoid atomically precise manufacturing and technology

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• Diffusion
• Water reactive gemstones

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• Atomically precise surface passivation

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• Well known scaling law: Rising surface area per volume of smaller machinery parts == Twice the surface area of half the volume

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• Hierarchical intentional breaking interfaces

External links

Wikipedia

• Corrosion
• Rust
• Passivation (chemistry)