The standard identifies four levels (designated as "rust grades" of mill scale and rust that are commonly found on surfaces of uncoated erected steel held in stock. It also identifies certain degrees of visual cleanliness (designated as "preparation grades") after surface preparation of uncoated steel surfaces and of steel surfaces after overall removal of any previous coating. These levels of visual cleanliness are related to the common methods of surface cleaning that are used prior to painting. The Standard is intended to be a tool for visual assessment of rust grades and of preparation grades.