This specification covers a premium aircraft-quality, corrosion- resistant steel in the form of sheet, strip, and plate. Primarily for parts requiring corrosion resistance approximating that of 18-8 type steels and strength exceeding that of 12Cr martensitic type steels up to 700 degrees F (371 degrees C). This steel can be used in the solution heat treated condition and can be precipitation heat treated to tensile strengths as high as 180 ksi (1241 MPa). This steel is relatively immune to stress-corrosion cracking, however reference should be made to ARP 1110 for recommended practices to minimize such conditions.