"GB/T 18570.8-2005 Test for the assessment of surface cleanliness of steel surfaces prepared before coating, Part 8: Field refraction determination of moisture" specifies a field assessment method for moisture (water) on the surface of steel before coating. This method measures the density of moisture on the surface of steel by refractometer. It is suitable for horizontal or slightly curved flat and vertical surfaces, not for surfaces exposed to rain or condensation. Standard equivalence adopts ISO 8502-8:2001, which is carried out by the China Shipbuilding Industry Group company and the National Coating and pigment Standardization Technical Committee of the metal surface preparation and painting process before painting. It was issued on September 14, 2005 and implemented on April 1, 2006.