The GB/T 8923.4-2013 standard specifies a visual assessment method for the surface cleanliness of steel before coating, in particular the initial surface condition, treatment grade and flash rust grade related to high voltage water jet treatment. The standard is suitable for evaluating the surface cleanliness of steel before and after high voltage water jet cleaning. It provides a quantitative basis for surface preparation mass before coating application through a clear grading and evaluation method. The implementation of the standard helps to improve coating adhesion and durability and ensure the long-term Reliability of the coating system.