Stainless steel corrosion resistance ranking

Classification of stainless steel and its corrosion resistance
Stainless steel can be divided into the following categories according to its metallographic structure:
‌Austenitic stainless steel‌: It is mainly composed of austenite with a face-centered cubic crystal structure, non-magnetic, and can be strengthened by cold working. Common models include 304 (200 and 300 series).
‌Ferritic stainless steel‌: It is mainly composed of ferrite with a body-centered cubic crystal structure, has magnetism, and usually cannot be hardened by heat treatment, but can be slightly strengthened by cold working. Common models include 430 and 446.
‌Martensitic stainless steel‌: It is mainly composed of martensite, has magnetism, and its mechanical properties can be adjusted by heat treatment. Common models include 410, 420 and 440.
‌Austenitic-ferritic (duplex) stainless steel‌: The matrix combines austenite and ferrite two-phase structures, has magnetism, and can be strengthened by cold working. Common models include 329.
‌Precipitation hardening stainless steel‌: Hardened by precipitation hardening treatment, common types include 630 (17-4PH).

The corrosion resistance ranking of stainless steel varies according to type and use environment.

Comprehensive corrosion resistance of various types of stainless steel: 

Austenitic stainless steel:
1Cr18Ni9Ti → 0Cr18Ni9 (304) → 0Cr18Ni11Ti (321) → 00Cr19Ni10 (304L) → 0Cr17Ni12Mo2Ti (316) → 00Cr17Ni14Mo2 (316L) → 00Cr19Ni13Mo3 (317L) → 00Cr20Ni25Mo4.5Cu (904L) → 00Cr27Ni31Mo4Cu
Ferritic stainless steel:
0Cr13 (410S) → 0Cr13Al (405) → 00Cr12Ti (409L) → 00Cr17 (430LX) → 00Cr18Mo2 → 00Cr26Mo1 → 00Cr30Mo2
Two-phase stainless steel:
00Cr18Ni5Mo3Si2 (3RE60) → 00Cr22Ni5Mo3N (SAF2205) → 00Cr25Ni7Mo4N (SAF2507) → 12Cr1MoV → 12Cr2Mo1 (2Cr-1Mo) → 1Cr5Mo → 1Cr9Mo → P91 (10Cr9Mo1VNb) → 0Cr25Ni20 (310S)