1.How to do anti-corrosion treatment after cutting, drilling and welding?
Damaged coating must be repaired: Any cutting, drilling, welding or severe scratching will damage the local zinc layer and expose the steel substrate. These areas will corrode first.
Secondary protection method: Special cold galvanizing paint (zinc-rich paint): First choice! Spray or brush on the damaged area, the zinc powder content must be ≥90% (in accordance with ISO 12944 standard), forming cathodic protection similar to hot-dip galvanizing.
Epoxy zinc-rich primer + topcoat: Used when the anti-corrosion requirements are extremely high or a specific color is required.
Processing requirements: The exposed metal surface must be thoroughly cleaned (degreasing, rust removal) to ensure coating adhesion. The coating should cover the damaged area and extend to the surrounding intact coating for at least 2cm.
2.What are the special requirements for welding work?
Ventilation is essential: Welding hot-dip galvanized steel will produce zinc-containing fumes, which are harmful to inhale. It must be operated in a strong ventilation environment, and the welder must wear a special gas mask (P100 grade filter element).
Remove the zinc layer in the weld area: Before welding, it is recommended to use a grinding wheel or special tools to grind off the zinc layer within 20-30mm on both sides of the weld, which can reduce pores and cracks and improve welding quality.
Post-weld cleaning and protection: Welding slag and spatter must be cleaned up, and the weld and heat-affected zone must be treated with secondary anti-corrosion according to Article 1.
3.What are the precautions for handling, lifting and storage?
Avoid coating damage: Use nylon slings or soft sheathed wire ropes for lifting. Do not use wire ropes to rub directly.
Handle with care during transportation to prevent collision and dragging that may cause the zinc layer to peel off or deep scratches.
Standard storage: Store in a dry, well-ventilated area to avoid water accumulation.
Use wooden strips to separate different specifications to prevent friction from damaging the coating.
Avoid mixing with corrosive substances such as strong acids, strong alkalis, and salts.
4.How to strengthen protection in special circumstances?
Strong corrosion environment (chemical plant, coastal area, high humidity): Even if the galvanized channel steel itself has good corrosion resistance, it is still recommended to spray the entire anti-corrosion topcoat (such as polyurethane, fluorocarbon paint) in extreme environments to provide double protection. Pay special attention to the sealing of weak points such as connection nodes and cuts.
Direct burial in soil: Ordinary hot-dip galvanized layer has a high corrosion rate in soil. When used directly, heavy anti-corrosion coating (such as epoxy coal tar) or sacrificial anode cathodic protection is required.
5.What should you pay attention to when cleaning surfaces and treating "white rust"?
Normal white rust, no need to panic: The grayish white powder (basic zinc carbonate) on the surface is a protective film naturally formed by the zinc layer, and no special treatment is required.
Stain cleaning: Use a neutral detergent + soft cloth/soft brush to clean, and do not use strong acids, strong alkalis or hard wire brushes. Oil stains can be wiped with organic solvents (such as alcohol).
Red rust = danger signal: The appearance of reddish-brown rust indicates that the substrate has been corroded, and it is necessary to remove the rust immediately and apply zinc-rich paint.