In order to ensure the coating quality of steel structure, the automatic shot blasting derusting machine is used for derusting. The sand blasting method uses compressed air to drive iron sand through special tools to spray on the metal surface at high speed. By using the impact and friction of iron shot, the rust and other pollution on the metal surface are removed, and a certain roughness is obtained,For the surface with exposed metal color, shot peening should be used to completely remove the black skin, rust and other external foreign matters, and then the dust and iron scale should be completely removed by vacuum cleaner or compressed air. The steel surface should be approximately gray white metal.After derusting and qualified by relevant personnel, the first primer shall be sprayed within 4 hours. 

Steel structure coating method

1、 Steel structure coating method

 　　1Steel structure primer coating:

 　　1.Mix the antirust paint, control the viscosity, consistency and thinness of the paint, and fully stir when cashing to make the color and viscosity of the paint consistent.

 　　2.When spraying the first layer of primer, the brushing direction shall be consistent and the joint shall be neat.

 　　3.When spraying paint, the principle of frequent moving and short moment separation is adopted to prevent too much spray paint from falling.

 　　4.After drying for the first time, spray the second time. The spraying direction of the second time is perpendicular to the direction of the first one, which will make the thickness of the paint film uniform.

 　　5.After spraying, the components shall be marked according to the original number, and the weight, center of gravity position and positioning mark shall be indicated for major components.

 　　2Finish painting of steel structure:

 　　1.The finish coating of steel structure shall be in accordance with the design requirements and shall not be changed at will. Attention shall be paid to the compatibility of the bottom and surface coatings.

 　　2.The finish coating of steel structure shall be carried out after the completion of field installation, and the dust and other foreign matters on the surface of steel structure shall be treated before painting the top coat of steel structure.

 　　3.The top coat with the same color shall be selected for top coat preparation. The thinner shall be suitable. The top coat shall be fully stirred before use to keep uniform color. Its working viscosity and consistency shall ensure that the steel structure will not drop and show brush marks during coating.

 　　4.The top coat should be continuously mixed in the process of steel structure coating, and the brushing method is the same as that of directional primer steel structure coating.

 2、 Precautions for steel structure painting:

 　　1Steel structure coating shall be carried out after the manufacturing quality is qualified

 　　2Before coating, the surface of steel structure shall be sandblasted to thoroughly remove dirt and oil and strictly remove rust; the rust removal grade shall reach SA2 specified in “rust grades and derusting grades of steel surfaces before coating of steel structures” (gb8923) 

Steel structure coating method

　　3After derusting, the steel members shall be sprayed with one coat of primer immediately, and then two finishing coats after maintenance (except for the components that need to be sprayed with fire-proof spraying materials); the surface of high-strength bolt joint, the steel member surface embedded in concrete and the full fusion welding range of 50 mm to be welded on site shall not be painted.

 　　4For the components sprayed with fire retardant coating, the fire retardant coating used shall comply with the provisions of the current national relevant specifications; the fire retardant coating shall be applied to the steel structure after installation, and the compatibility test shall be conducted between the selected fire retardant coating and the primer, and it can be used only after passing the test.

 3、 Inspection and acceptance of steel structure coating:

 　　1.Steel structure coating after treatment inspection, should be the steel structure coating color is consistent, bright color, not Zou skin, not pimple.

 　　2.During and after the surface steel structure coating construction, the steel structure coating work shall be protected to prevent dust and other debris.

 　　3.The thickness of coating film of steel structure is measured by corner point type paint film thickness meter. Generally, the thickness of three points is measured by paint film thickness gauge, and the average value is taken.