If you look at the spec sheet in the picture library, it seems like the 4 most expensive materials (gold, platinum, silver, rhodium) are electroplated rather than cnc engraved solid elements like the rest of them.
Are the Cu and Ag keycaps (copper & silver) clear coated to prevent them from getting a patina/ slowly corroding (oils from fingers would accelerate this process)?
Awekeys has applied thick layers of antioxidant protection coatings on the surface of each keycap, so the keycaps should be fine with daily use, and should not corrode over time.