1.What are the requirements for galvanized steel materials in high-rise buildings?
Zinc layer thickness/quality: The standard specifies the minimum local zinc layer thickness or minimum coating quality requirements per unit area for different steel thicknesses. High-rise buildings usually require a higher level of corrosion protection and may require a thicker zinc layer (for example, higher than the standard requirements), which needs to be clarified during design and procurement.
Appearance quality: The coating should be continuous, uniform, smooth, without missing plating, sagging, zinc nodules (or zinc nodules within the allowable range), peeling, inclusions, and other defects that affect the anti-corrosion performance or appearance.
Adhesion: The coating should have good adhesion and is not easy to peel off during transportation, handling, processing and installation.
2.What are the design requirements for using galvanized steel in high-rise buildings?
Structural design: Structural design must meet the requirements of the ultimate bearing capacity state and the normal use limit state, taking into account the slight increase in component size caused by galvanizing (usually 50-100 microns per side, which can be ignored).
Avoid liquid accumulation: Component design should avoid the formation of closed spaces or grooves that are prone to water accumulation, to prevent the residual acid or water after galvanizing from being unable to be discharged, resulting in "white rust" corrosion or internal corrosion. Drain holes and vents should be designed.
Connection design: Pay special attention to the effect of galvanizing on friction-type high-strength bolt connections and welding connections.
3.What are the requirements for using galvanized steel storage in high-rise buildings?
Store in a dry, well-ventilated area, preferably indoors or under a shed.
When stored outdoors, it should be elevated (>200mm from the ground) and covered tightly with waterproof cloth to prevent water accumulation.
Components of different specifications and lengths should be classified and stacked neatly to avoid mutual compression that may cause deformation or damage to the coating.
Avoid direct contact with metals such as copper, brass, and stainless steel (which may cause galvanic corrosion).
4.What precautions should be taken during on-site installation?
Protection: During installation, the galvanized layer must be continuously protected from damage (scratches, collisions, welding spatter, etc.).
Welding: On-site welding must strictly follow the welding process regulations for galvanized steel, and ventilation and personal protection must be done well (to prevent zinc fume poisoning). The damaged area must be immediately treated with the prescribed anti-corrosion treatment after welding (see point 4).
Bolt connection: Install friction-type high-strength bolts according to design requirements to ensure that the specified pre-tension is achieved. Pay attention to protecting the galvanized layer of the bolts (if any) and the friction surface of the connecting plate.
Avoid contact: Galvanized steel components should avoid direct contact with ungalvanized ordinary carbon steel and concrete (especially newly poured wet concrete) to prevent galvanic corrosion or corrosion of zinc by alkaline substances in concrete. Insulating gaskets (such as nylon, rubber, neoprene gaskets) or coatings should be used for isolation.
Avoid water accumulation: After installation, ensure that the designed drainage holes and vents are unobstructed, and no long-term water accumulation areas are formed on the components.
5.What are the requirements for testing and quality control?
Galvanized layer inspection: Factory inspection: The galvanizing plant should provide a quality certificate for each batch of products, including substrate information, coating thickness (magnetic thickness measurement method), appearance inspection results, adhesion test results (such as hammer test), and compliance standards.
On-site re-inspection: The construction unit or supervision unit should conduct sampling re-inspection of the galvanized steel components entering the site. The inspection items usually include: Appearance quality (visual inspection)
Coating thickness (magnetic thickness gauge spot check)
Product warranty verification
Post-weld repair inspection: Visual inspection and thickness inspection (dry film thickness gauge) of the anti-corrosion coating repaired after welding