There are numerous ‘types’ of stainless steel, with each type formulated for specific properties such as ease of fabrication, machinability, weldability, atmospheric corrosion resistance, etc. These types range from 100 Series austenitic chromium-nickel-manganese alloys to 600 Series martensitic precipitation hardening alloys, to Type 2205 duplex ferritic/austenitic alloy. The term ‘stainless steel’ covers many, many alloys, and the performance of each alloy will be unique to that alloy.
The two most common types are the 300 Series austenitic chromium-nickel alloys and the 400 Series ferritic and martensitic chromium alloys. Generally speaking, the 300 series (types 304 & 316 are the most common) have excellent corrosion resistance, with no visible ‘rusting’ when exposed to atmospheric moisture. They are relatively hard to fabricate, with specialized cutting and welding required.
Some of the type 400 series have a higher iron content (thus the name “ferritic”), with many of them being slightly magnetic. These materials are somewhat easier to fabricate and to perform special manufacturing operations such as hardening. Use in cutlery is one example of type 400 SS. Many 400 series stainless steels also exhibit a higher degree of effect from atmospheric corrosion: Some say they ‘rust’.
On a relative scale, all stainless steel alloys are significantly less effected by atmospheric corrosion than corresponding steel alloys, but it is very possible to find some ‘rust’ on stainless steel.
Happy RRing,
Jerry