The corrosion resistance mechanism of A423 weathering steel relies on the formation of a protective rust layer (patina) through deliberate alloy design and atmospheric exposure. Here's a concise breakdown:
1. Protective Patina Formation
Alloying Elements (Cu, Cr, P, Ni):
React with oxygen/moisture to form a dense, adherent rust layer (FeOOH), acting as a barrier against further corrosion.
Cu (0.25–0.55%) and Cr (0.30–1.25%) stabilize the patina, while P accelerates early-stage oxidation.
2. Self-Healing Ability
Minor damage (e.g., scratches) re-oxidizes naturally, reforming the protective layer in wet/dry cycles.
3. Key Limitations
Chlorides/Salt: Disrupt patina in coastal environments (requires coatings).
Industrial SO₂: Tolerates moderate pollution but may slow patina formation.
