1.How does the zinc layer perform in different temperature ranges?
≤149℃: The zinc layer is stable and the oxidation rate is extremely slow.
149~200℃: The zinc layer begins to soften and the wear resistance decreases; corrosion accelerates in a wet environment.
200~300℃: Zinc-iron diffusion intensifies → the alloy layer thickens and becomes brittle; the surface zinc oxide (ZnO) is grayish white
300~419℃: Precursor of zinc layer melting (local blistering and peeling); large amounts of zinc oxide are generated
≥419℃: The zinc layer completely melts and loses; toxic zinc oxide fumes are released
2.What are the differences between different galvanizing processes?
Conventional hot-dip galvanizing: long-term safety temperature ≤120℃; short-term peak temperature ≤200℃; high-temperature failure characteristics are powdering and peeling of the zinc layer.
Electrogalvanizing: long-term safety temperature ≤80℃; short-term peak temperature ≤150℃; high-temperature failure characteristics are blistering and cracking of the coating.
Zinc-aluminum coating: long-term safety temperature ≤180℃; short-term peak temperature ≤250℃; high-temperature failure characteristics are aluminum inhibiting diffusion and delaying failure.
Zinc-nickel alloy coating: long-term safety temperature ≤220℃; short-term peak temperature ≤300℃; high-temperature failure characteristic is that nickel improves thermal stability.
3.What are the countermeasures for high temperature environment?
Anti-corrosion protection upgrade
200~300℃: spray inorganic zinc-rich paint (resistant to 400℃) or silicone heat-resistant paint (resistant to 300℃)
＞300℃: the zinc layer must be removed and replaced with hot-dip aluminum (resistant to 600℃) or zinc treatment (resistant to 500℃)
Welding protection: Apply high temperature zinc-based repair paste (resistant to 260°C) to the weld area to prevent zinc burning in the heat-affected zone
4.What are the failure cases and solutions?
Solar bracket (surface temperature 80~110℃)
Problem: Zinc layer powdered and red rust penetrated after 5 years
Solution: Use zinc aluminum magnesium coated steel sheet (ZAM) + apply sealant at the joints
5.Any practical suggestions?
Continuous working temperature > 120°C Avoid using galvanized steel Short-term heat exposure (< 1 hour) can be relaxed to 200°C, but the integrity of the zinc layer needs to be checked after cooling