The rust level for steel product surface

There are 4 levels for the rust of steel product surface
1. covered by large area oxidation layer nearly without rust.
2. rust has occurred and oxidation layer starts falling.

3. oxidation layer has rusted and fell, or rust layer can be scraped, but steel surface, which has some rust spots, can be observed with the naked eye.

4. oxidation layer has rusted and fell, or rust layer can be scraped, but steel surface, which has a lot of rust spots, can be observed with the naked eye.