Bearings
Water/Rust Testing
Most videos on youtube do a poor job in testing bearings in water. They do in fact often get the rust process correct by half submerging the bearings in water, because it needs oxygen from the air to truly rust
However, They look at the rust on the outer side of the races as proof the bearings are rusted inside. The issue is that the grease/oil around the ball bearigns provides a protective layer on the bears that prevent rust and the seal itself (rubber or metal) also provides a good barrier...
So in real life the bearings (steel or ceramic) do not really get rusted on the inside much. So generally safe to just go with steel tbh.
The one good video I found is this one:
However, the high end cycling bearings (like enduro?) actually use a higher grade stainless steel (more chromium I believe) in the 400 series, rather than the 300 series. These seem to even protect against rust on the outer side of the races when introduced to water/air for extended periods of time.
Unusure how expensive or if available for small form used in skating...