1. Corrosion mechanism difference
Carbon steel (Q235, Q355, SS400 etc.)Rust layer is loose, porous, and easy to fall off.Moisture and oxygen keep penetrating inward, so corrosion accelerates continuously until perforation.
Q460NH weathering steelContains alloy elements (Cu, Cr, Ni, P) that form a dense, tight, adhesive patina on the surface.This layer blocks corrosion mediums and makes the corrosion rate drop sharply to a very low stable level.
2. Corrosion rate comparison
Under the same unpainted outdoor atmosphere:
Q460NH corrosion rate: only about 1/5 to 1/8 of carbon steel
Carbon steel rusts through in a few years; Q460NH can be used stably for decades
3. Performance in different environments
Rural / urban / industrial atmosphereQ460NH: excellent, stable patina, almost no deep corrosionCarbon steel: severe rust, obvious thickness loss
High humidity, poor ventilationQ460NH: corrosion slows down but still better than carbon steelCarbon steel: extremely fast corrosion
Coastal salt-spray areaBoth become worse, but Q460NH still performs obviously better than carbon steel
Water immersion / buriedBoth lose effective protection, but Q460NH still has slightly better resistance
4. Surface state difference
Carbon steel: loose yellow-red rust, serious runoff, easy to stain surrounding materials
Q460NH: gradually forms dark brown stable patina, little to no runoff
