Derusting quality grade of steel structure

Derusting method of grade quality standard

　　1.Steel surface exposed to metal color sandblasting, shot blasting, pickling

　　2.It is allowed to keep clean rolling surface on the steel surface. General tools (wire brush, emery cloth) shall be removed

　　3）In order to ensure the coating quality, the following rust removal processes can be selected according to different needs.

Sand blasting derusting is a kind of derusting method that uses the pressure of compressed air to continuously impact the surface of steel members with quartz sand or iron sand, clean up the rust, oil and other sundries on the steel surface, and expose the true color of metal steel.This method has high efficiency and thorough rust removal. It is an advanced rust removal process.

Pickling is to dip the steel members to be coated into the acid tank and remove the oil and rust on the surface of the members with acid.The efficiency of pickling process is also high and the rust removal is thorough. However, after pickling, the components must be washed with hot water or clean water. If there is residual acid, the components will be more severely rusted.

Manual derusting is to remove the rust on the steel members by manually using some simple tools, such as scraper, grinding wheel, emery cloth, wire brush, etc.This method has low efficiency, poor working conditions and incomplete rust removal.

　　3.Primer application:

　　1）Prepare red lead antirust paint, control the viscosity, consistency and thinness of the paint, and fully mix when cashing to make the paint color and viscosity uniform.

　　2）When the first primer is applied, the direction of application shall be the same and the joints shall be neat.

　　3）When painting, the principle of frequent touch and short brush shall be adopted to prevent the brush from falling due to too much paint.

　　4）After the first painting, a certain time interval shall be maintained to prevent the second painting before the first painting is dry, which will make the paint liquid flow wrinkle and reduce the quality.

　　5）After the first drying, brush the second time. The direction of the second painting shall be perpendicular to the direction of the first painting, so as to make the film thickness uniform.

　　6）At least 4-8h after the primer is applied, it can reach the surface drying, and the top coat shall not be applied before the surface drying.

　　4.Finish painting:

　　1）In general, the interval between primer and finish coat of steel structure is long.Steel members shall be sent to the construction site for assembly after being coated with antirust paint, and the finishing coat shall be applied uniformly after assembly.In this way, the surface of steel structure shall be cleaned before finishing, the welding flux of installation weld shall be removed, and the components burnt or touched with paint shall be repaired in advance.

　　2）The top coat with the same color shall be selected for the preparation of the top coat, and the prepared diluents shall be suitable. The top coat shall be fully stirred before use to keep the color uniform.Its working viscosity and consistency shall ensure that there is no sagging and brush marks during painting.

　　3）The finishing coat shall be continuously mixed during use, and the method and direction of application shall be the same as the above process.

　　4）When spraying construction is adopted in the coating process, the nozzle diameter and spraying pressure shall be adjusted. The spray gun hose can be freely stretched to the operation area, and the air pressure of the air compressor shall be 0.4-0.7n/m2

　　5）The distance between the spray nozzle and the coating shall be kept well during spraying. Generally, the distance between the spray gun and the working surface shall be about 100 mm. The angle between the spray gun and the base surface of the steel structure shall be vertical, or the spray nozzle shall be slightly inclined upward.

　　6）During spraying, the nozzle shall move in parallel, and the movement shall be stable, the speed shall be consistent, and the coating shall be uniform.However, when spraying is adopted, the thickness of the general coating is relatively thin, so it should be sprayed several times more, and each spraying should be carried out when the upper paint film has dried.

　　5.Coating inspection and acceptance:

　　1）During and after the surface coating construction, the coated workpieces shall be protected to prevent dust and other sundries from flying.

　　2）The treatment inspection after coating should be the same color, bright color, no wrinkle, no pimple.

　　3）For the measurement of coating film thickness, the contact type film thickness gauge is used to measure the film thickness, and the film thickness gauge generally measures the thickness of three points, taking the average value.