The ISO 8504-4:2022 standard describes picking as an effective method for surface preparation of steel substrates for cleaning steel prior to coating paints and related products. This method is widely used to remove rust, mill scale and Miscellaneous contaminants from steel surfaces, especially for steel surfaces that may deform after sand blasting cleaning. The acidic solution used in the picking process often contains inhibitors to control the rate of corrosion of metals while removing rust and impurities. This method is particularly suitable for new steel structures, but does not include cleaning equipment surfaces or cleaning requirements for specific purposes. The purpose of the standard is to ensure that the surface condition of the steel meets the specified cleanliness standards before painting to ensure the performance and durability of the coating.