Steel structures are often sprayed with zinc or aluminum, and long-term anti-corrosion structures are formed with heavy-duty anti-corrosion coatings, or coated with matching heavy-duty anti-corrosion coatings for protection. Metal zinc and aluminum have good atmospheric corrosion resistance. Spraying zinc or aluminum on steel components, zinc and aluminum are negative potential, and steel forms sacrificial anode protection, so that steel is basically protected. At present, sprayed aluminum coating is used to prevent the corrosion of industrial atmosphere and marine atmosphere, which is characterized by: (1) strong bonding force between sprayed aluminum coating and steel matrix, long coating life and good long-term economic benefits; (2) The process is flexible, suitable for long-term protection of important large-scale and difficult-to-maintain steel structures, and can be used for on-site construction; (3) The coating sprayed with zinc or aluminum and sealed with antirust paint can greatly prolong the service life of the coating. From the theoretical and practical application results, the coating sprayed with zinc or aluminum is the best primer for anti-corrosion coatings. The protective life of the composite coating of metal spray coating and anti-corrosion coating is longer than the sum of the life of metal spray coating and anti-corrosion coating, and is several times that of a single coating. Heavy-duty long-lasting anticorrosive coating consists of primer, intermediate paint and topcoat. Considering the long-term economy, aluminum spraying coating is the most economical, but the one-time investment is large, and the well-constructed coating can be maintained within 10 years. Epoxy zinc-rich primer+epoxy micaceous iron intermediate and acrylic polyurethane long-term protection system are more economical.

See the specification and atlas for specific contents, or ask the design institute for specific analysis.

4.3. 1 When the corrosion grade is strong or medium, lattice and cold-formed thin-walled steel beams should not be used for important mechanical components such as trusses, columns and main beams.

4.3.2 The selection of steel structure bar section shall meet the following requirements:

1 bar should adopt solid abdomen or closed section, and the end of closed section should be closed; Explosion-proof measures should be taken when hot galvanizing in closed section.

2 when the corrosion grade is strong or medium, T-shaped section composed of double angle steel or I-shaped section composed of double channel steel should not be adopted; When the corrosion level is weak, the above T-shaped or I-shaped section should not be adopted.

3. When steel bars are used, the gap width between steel bars should meet the requirements of protective layer construction and maintenance.

4.3.3 The section thickness of steel structure bars shall meet the following requirements:

1 steel plate combined rod, not less than 6mm.

2 closed profile, not less than 4 mm ..

3 Angle steel section thickness is not less than 5 mm ..

4.3.4 Portal frame members should adopt hot-rolled H-beam, and when T-beam or steel plate combination is adopted, double-sided continuous weld should be adopted.

4.3.5 The grid structure shall adopt tubular section and ball joints, and shall meet the following requirements:

When the corrosiveness of 1 is strong or medium, welded hollow ball joints should be adopted.

2 When bolt ball joint is used, the joint between rod and bolt ball should be filled with sealing material, and the redundant bolt holes should be blocked.

4.3.6 Isolation measures should be taken for the contact parts of different metal materials.

4.3.7 Welds of important steel members such as trusses, columns, main beams and closed section steel shall be continuous. The leg size of fillet weld should not be less than 8 mm; When the steel bar thickness is less than 8 mm, the size of the welding leg should not be less than the steel bar thickness.

Stiffening ribs should be chamfered; The cutting angle should meet the requirements of drainage, construction and maintenance.

4.3.8 The corrosion resistance of covered electrode, bolts, washers, gusset plates and other connectors shall not be lower than that of the main material. Bolt diameter should not be less than 12mm. Washers should not be spring washers. Bolts, nuts and washers should be protected by hot dip galvanizing, and the same anti-corrosion measures as the main structure should be taken after installation.

4.3.9 The derusting grade of the contact surface at the joint of high-strength bolt members shall not be lower than SA2. 1/2, and it shall be coated with inorganic zinc-rich coating; Joint gap should be embedded with anti-corrosion sealing paste.

4.3. The foot of10 steel column should be placed on the concrete foundation, and the top surface of the foundation should be not less than 300mm from the ground.

4.3. 1 1 When the corrosion grade is strong, the important components shall be made of weathering steel.