MIL-STD-1568C
Cadmium plated surfaces shall not be used in applications where surface temperature exceeds
450 °F (232 °C). Cadmium shall not be used on functional fuel systems components that can come into contact with fuel during operations of the aircraft. Cadmium plated fasteners, used in areas where contact with fuel can occur, shall be overcoated with an approved fuel tank sealant and coating over the sealant. Chromium plating shall be considered an acceptable corrosion prevention for alloy steel wear surfaces only when the chrome plating is periodically lubricated (fluid or grease types only) or a 0.038 mm (0.0015 inch) minimum layer of nickel plating is applied under the chromium. All chromium plated steel parts used in fatigue application shall be shot peened prior to plating. Chromium plated surfaces shall not be used in applications where service temperatures exceed 700 °F (371 °C).
5.2.3.2.2 Stress corrosion factors. Alloy steel parts heat treated to 1241 MPa (180 ksi) UTS and above shall be designed, manufactured, assembled, and installed such that sustained residual surface tensile stresses shall be minimized to prevent premature failures due to stress corrosion cracking. The use of press or shrink fits, taper pins, clevis joints in which tightening of the bolt imposes a bending load on the female lugs, and straightening or assembly operations that result
in sustained residual surface tensile stresses in these materials shall be avoided. In cases where such practices cannot be avoided, protective treatment such as stress relief heat treatments, optimum grain-flow orientation, wet installed (with a protective material) inserts and pins, and shot peening or similar surface working to minimize the hazard of stress-corrosion cracking or hydrogen embrittlement damage shall be applied.
5.2.3.3 Corrosion resistant steels. All corrosion resistant steels shall be passivated in accordance with SAE AMS2700 or ASTM A380. In addition, 400 series martensitic steel require coatings for protection against corrosion. Table II should be used as a guide in the selection of corrosion resistant steels for structural applications.
5.2.3.3.1 Corrosion resistant steels limitations. Precipitation hardening steels shall be aged at temperatures not less than 1000 °F (538 °C). Exception is made for castings which may be aged at 935 °F ±15 °F (501.5 ±9.4 °C), for fasteners which may be used in the 950 condition, and for springs which have optimum properties at the CH 900 condition. Corrosion resistant maraging steels shall not be used in sustained load applications. Corrosion resistant 19-9DL and
431 steels shall not be used for any applications. Series 500 martensitic grade corrosion resistant steels shall not be used in the 700 °F to 1100 °F tempered condition. Unstabilized austenitic steels may be used up to 700 °F (370 °C). Only stabilized austenitic steels (321 and 347) shall be used above 698 °F (370 °C). All welded or brazed austenitic steel shall be solution heat treated after welding; however, welded 321 and 347, 304L and 316L may be used without heat
treatment.
5.2.3.4 Titanium.
5.2.3.4.1 Surface considerations. The surfaces of titanium mill products (sheet, plate, bar, forging, casting and extrusion) shall be 100 percent machined, chemically milled, or pickled to remove all contaminated zones and layers formed while the material was at elevated temperature. This includes contamination as a result of mill processing, heat treating and elevated temperature forming operations.
8
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business