5.7　Paining

5.7.1　The surface rust removal of steel products before painting shall not only comply with the design requirements but also the requirements in GB/T 8923.1 Preparation of Steel Substrates before Application of Paints and Related Products-Visual Assessment of Surface Cleanliness-Part 1:Rust Grades and Preparation Grades of Uncoated Steel Substrates and of Steel Substrates after Overall Removal of Previous Coatings.After treatment，the surface of steel products shall not have any welding slag，welding scar，dust，oil stain，water，burr，etc.，If the design does not make such requirements，the rust removal method and grade shall fit with the paint（s）required by the design.

Sample size:10% of all components，and at least 3 pieces for the same type of components.

Check method:Checking with scraper knife or visual inspection according to the pictures provided in current national standard GB/T 8923.1 Preparation of Steel Substrates before Application of Paints and Related Products-Visual Assessment of Surface Cleanliness-Part 1:Rust Grades and Preparation Grades of Uncoated Steel Substrates and of Steel Substrates after Overall Removal of Previous Coatings.

5.7.2　The paint variety，painting courses and painting thickness shall comply with the design requirements.If the design does not make any requirement on painting thickness，the total number of painting courses of the main steel structure should be 4.Two courses of primer painting and one course of top painting should done by the manufacturer；after the components are installed and splice-welded on the site，one more course of top painting should be applied.The total thickness of dry film of the paint layer shall not be less than 80μm indoor and not be less than 100μm outdoor.

Sample size:10% of all components，and at least 3 pieces for the same type of components.

Check method:Measuring with dry paint film thickness gauge.Four（4）places shall be tested for each component，and the thickness value of each place should be the mean thicknesses of dry paint film of 3 measuring points at the spacing of 50mm.

5.7.3　The surface of components shall be free of miss painting and void，of any painting peeling and rerusting.In addition，the painting shall be even and free of obvious wrinkle，flow fall，needle hole and blowhole.

Sample size:100%.

Check method:visual inspection.

5.7.4　The spot（s）where the construction drawing indicates that no painting be applied shall not be coated.In addition，a length of 30 to 50 mm shall be reserved uncoated temporarily for field welding.