Generally speaking, the surface treatment of structural steel plates is needed to increase their anti-corrosion and durability. The quality of surface treatment directly affects the adhesion of the coating to the substrate of the coated workpiece and the corrosion resistance of the material. Oil, grease, dust and other contaminants will cause the paint film to fall off or produce a variety of appearance defects, anticorrosive coating can improve the anticorrosive protection of the paint layer on the steel plate and the smooth surface of the base steel. Common anticorrosive coatings require a substrate surface cleanliness of SA2.5 or above, and steel plate surface coatings provide excellent corrosion protection for the water treatment industry, pulp and paper mills, Bridges and offshore facilities.
According to the design and drawings, the anti-corrosion coating on the exposed part of the bridge support and the shock-absorbing steel plate is treated to prolong its service life. The main construction method is epoxy zinc-rich primer construction, according to the requirements of the design position of the steel plate to achieve protection purposes. The process includes base surface cleaning → primer coating (epoxy zinc-rich primer 50μm, 2 times) → finish coating (modified polyurethane topcoat 50μm, 2 times) → inspection and acceptance. The supporting plan of coating is as follows:
|Items||Coat painting||Color||Paint film thickness||Theoretical paint (g/m2)||Coating interval(20℃)|
|Surface treatment||The surface should be strictly derusting with a quality standard Sa2.5|
|First layer （2times）||Epoxy zinc rich primer-conventional 50% zinc||Grey||80-100μm||40-50μm/time||1～7days|
|Second layer （2times）||Anticorrosive topcoat-modified polyurethane topcoat||Green||80-100μm||40-50μm/time||1～7days|
The base surface cleaning
Before the paint is brushed, the coating and rust of the exposed part of the steel plate of the support and the shock absorber plate are polished off with an Angle grinder. The quality standard for rust removal is SA2.5.
Primer coating (epoxy zinc-rich primer 50μm, 2 coats)
1) Epoxy zinc-rich primer, according to the ratio of 9∶1 and control the viscosity of the paint, the system should be fully stirred, so that the paint color and viscosity is uniform, curing 25 ~ 30 minutes, the paint needs to be used up within 4 ~ 6 hours.
2) Brush the first layer of primer brushing direction should be consistent, neat. Apply multiple times to prevent the brush from running too much paint.
3) Maintaining a certain time after the first brush, to prevent paint not dry paint flow drop. Brush the second time after the first drying. The direction should be perpendicular to the first time and the film thickness should be uniform.
Finish coating(modified polyurethane finish 50μm, 2 times)
1) Top paint is green. The finish coat should be made of a modified polyurethane finish of the same color, in accordance with the appropriate proportion. Full mixing before use and uniform color to ensure that the coating does not fall, do not show grain.
2) The method and direction should be the same as the above process.
3) The coating interval between top coat and primer should be more than 2 days.