2. Carbon Steel, Low Alloy Steels
<2% other elements (Cu, Ni, Si, Cr)
Low corrosion resistance
Tanks, Pipes, Buried structure, Concrete, ship hulls, piers, offshore structures
Passive in alkaline pH
Coating, cathodic protection
Subject to hydrogen cracking in petroleum indutry

3. Stainless Steel at least 10.5% Cr Classification Ferritic Austenitic
Duplex
Martensitic
Precipitation Hardening

4. Ferritic Cr + Mo (sometimes) Cr stabilizes ferrite Susceptible to IGC
Immune to Chloride SCC
Used in thin wall tubes-heat exchanger tubes
Example SS405, SS 409, SS 430 ( architectural, automobile trimming)
Elevated temp applications

5. Austenitic Steel Cr + Ni Cr-rich passive layer
Chloride attack causes pitting, crevice and SCC
SS 304, SS 316, SS317
Can handle H2S containing environments
Used in valves, pumps, fasteners, screens,
Process vessels, piping, etc

6. Martensitic and Precipitation Hardening SS
Duplex
Cr-Mo Alloys with Austenitic stabilizers like Ni and N
Mixture of Ferritic and Austenitic Steels
Mo strengthens the passive layer formed by Cr.
Martensitic and Precipitation Hardening SS
Good mechanical strength
Lower corrosion resistance
Susceptible to HIC and SCC

10. Designing to Prevent Corrosion
Design Philosophy
Process Variables
Corrosion Data
New Materials and Equipment Design