SUS420 Stainless Steel: Corrosion Resistance & Hardness

: It's a medium-carbon, high-hardenability steel designed for excellent hardness, reaching up to 50+ Rockwell C (HRC).

: Achieves maximum hardness through hardening and tempering, providing superior wear resistance.

: Offers good resistance in fresh water, food, mild acids/alkalis, steam, and crude oil when hardened and polished.

: Best corrosion resistance comes from a ground or polished surface; scale and dirt reduce protection.

: Performance drops above 400℃ (750℃F), with strength loss and reduced corrosion resistance.

: Knives, surgical/dental instruments, scissors.

: Pump/valve parts, gears, bearings, springs, shafts.

SUS420 balances hardness and corrosion resistance, but its high-carbon martensitic structure means you sacrifice some toughness and high-temp performance for extreme hardness, requiring specific finishing (polishing/hardening) for optimal protection.