MIL-STD-1568 Materials And Processes For Corrosion Prevention And Control In Aerospace Weapons SystemsThis standard establishes the requirements for materials, processes and techniques, and identifies the tasks required to implement an effective corrosion prevention and control program during the conceptual, validation, development and production phases of aerospace weapons systems. The intent is to minimize life cycle cost due to corrosion and to obtain improved reliability.

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MIL-STD-1568C

attention shall be given to precautionary measures to minimize deterioration of individual parts and assemblies as well as the entire system. Required precautionary measures are specified in

5.2.2 through 5.2.4.

5.2.2 General design guidelines for corrosion prevention.

5.2.2.1 Exclusion of rain and airborne spray. The design of the system shall prevent water leaking into, or being driven into, any part of the system interior either on the ground or in flight. All windows, doors, panels, canopies, etc. shall be provided with scaling arrangements such that the entry of water is minimized when these items are correctly closed. Particular care shall be taken to prevent wetting of equipment, thermal insulation, and sound proofing materials. Recesses should be avoided so that moisture and solid matter cannot accumulate to initiate localized attack. Sealed floors shall be provided for galleys, toilets, and cockpits. Suitable drainage shall be provided for cockpits.

5.2.2.2 Ventilation. Ventilation shall prevent moisture retention and buildup.

5.2.2.3 Drainage. Drain holes shall be provided to prevent collection or entrapment of

water or other unwanted fluid in areas where exclusion is impractical. Minimum diameter for all drains shall be 9.525mm (.375 inch) unless otherwise approved by the procuring activity. All designs shall include considerations for the prevention of water or fluid entrapment and ensure that drain holes are located to permit maximum drainage of accumulated fluids. Actual aircraft configuration and attitude shall be considered in addition to component design.

5.2.2.4 Dissimilar metals. Use of dissimilar metals, as specified in MIL-STD-889, in contact shall be limited to applications where similar metals cannot be used due to design requirements. When it is necessary to use dissimilar metals in contact, the metals shall be protected against galvanic corrosion. Galvanic corrosion can be minimized by interposition of a material that reduces the overall electrochemical potential of the joint or by interposition of an insulating or corrosion-inhibiting material. Composite materials containing graphite fibers shall be treated as graphite in MIL-STD-889.

5.2.3 Metallic materials.

5.2.3.1 Aluminum.

5.2.3.1.1 Alloy selection. The selection of aluminum alloys for structural application requires consideration of their resistance to stress-corrosion cracking (SCC). Maximum use shall be made of alloys and heat treatments that minimize susceptibility to SCC. Relative SCC ratings for high strength aluminum alloy products based on ASTM G64 and service experience are specified in table I. Although the ratings are based primarily on the results of standard corrosion tests, an experience factor can be substituted for those materials that have established service records. The ratings are given for the Short Transverse Grain Direction (STGD) since this is the most critical SCC condition in structural applications.