P5 (P5, WP5, F5) (5%Cr • 1/2%Mo)
P5 is a chromium alloy used for its strong resistance to hot sulfide corrosion cracking. 5% chromium material has a higher minimum mechanical properties than 1 1/4% and.
P9 (P9, WP9, F9) (9% Cr • 1% Mo)
Used primarily for Nace applications where sour environmentals under high temperature and pressure are expected. Chromium of 9% gives corrosion resistance similar to 400 series.
P11
“Low alloy” refers to steel with an alloy composition of 1 to 1 1/2% chromium and molybdenum. The small amount of chromium and molybdenum differentiates.
P22 (P22, WP22, F22) (2 – 1/4% Cr • 1% Mo)
Used primarily for their stress/rupture properties, P22 can be held at high temperatures with high pressure and can also have a strong resistance to rupturing..