"GB/T 18570.9-2005 Assessment of surface cleanliness of steel surface preparation before coating, Part 9: Field conductivity determination of water-soluble salts" specifies a field assessment method for the total surface concentration of water-soluble salts (mainly chlorides and sulfates) on the surface of steel before and after surface pretreatment. This method evaluates the ionic impurity concentration on the surface of steel by conductivity measurement and is not suitable for the determination of chlorides or sulfates alone. Standard equivalence adopts ISO 8502-9:1999, which is under the jurisdiction of China Shipbuilding Industry Group company, National Coating and pigment Standardization Technical Committee for metal surface preparation and painting process before painting, issued on September 14, 2005, and implemented on April 1, 2006.