1、MILITARY STANDARD DISSIMILAR METALS FSC MFFP Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-BBqB CHG NOTICE 3 m 9799913 0434333 L99 M TO ALL I IOLDERS OF MILITARY STANDARD DISSIMILAR METALS MIL-STD-889B: NOT MEASUREMENT SENSITIVE MIL-STD-889
2、B NOTICE 3 (USAF) 17 May 1993 1. THE FOLLOWING PAGES OF MIL-STD-889B HAVE BEEN REVISED AND SUPERSEDE THE PAGES LISTED: NEW PAGE DATE SUPERSEDED PAGE DATE a 3 21 November 1979 - REPRINTED WITHOUT CHANGE 4 17 May 1993 4 7 July 1976 2. RETAIN THIS NOTICE AND INSERT BEFORE TABLE OF CONTENTS. 3. Holders
3、of MIL-STD-889B will verify that page changes and additions indicated above have been entered. This notice page will be retained as a check sheet. Ths issuance, together with appended pages, is a separate publication. Each notice is to be retained by stocking points until the military standard is co
4、mpletely revised or cancelled. Custodians: Air Force - 11 Review activities: Air Force - 13, 17, 99 Preparing activity: Air Force - 11 O AMSC: N/A AREA: MFFP DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Provided by IHSNot for ResaleNo reproduction or networking p
5、ermitted without license from IHS-,-,-r= MIL-STD-889B NOTICE I GD m 7779933 0035273 8 m MIL-STD-889B NOTICE 1 21 November 1979 MILITARY STANDARD DISSIMILAR METALS TO ALL HOLDERS OF MIL-STD-889B: 1. THE FOLLOWING PAGES OF MIL-STD-889B HAVE BEEN REVISED AND SUPERSEDE THE PAGES LISTED: NEW PAGE DATE SU
6、PERSEDED PAGE DATE 1 7 July 1976 (REPRINT WITHOUT CHANGE.) 7 July 1976 2 21 November 1979 2 7 July 1976 3 21 November 1979 3 7 July 1976 4 7 July 1976 (REPRINT WITHOUT CHANGE) 7 July 1976 5 21 November 1979 5 7 July 1976 6 21 November 1979 6 7 July 1976 2. RETAIN THIS NOTICE AND INSERT BEFORE TABLE
7、OF CONTENTS. 3. Holders of MIL-STD-889B will verify that page changes and additions indicated above have been entered. This notice page will be retained as a check sheet. This issuance, together with appended pages, is a separate publication. Each notice is to be retained by stocking points until th
8、e Military Standard is completely revised or canceled. .Custodians : Navy - AS Air Force - 11 Army - MX Review activities: Army -AR Navy - EC, OS Air Force - 13, 17, 99 Preparing activity: Air Force - 11 FSC MFFP Provided by IHSNot for ResaleNo reproduction or networking permitted without license fr
9、om IHS-,-,-DEPARTMENT OF DEFENSE . ii Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Paragraph l. 1.1 1.1.1 2. 2.1 3. 4. 5. 5.1 5.2 MIL-STD-889B 7 July 1976 CONTENTS TABLES Appendix A. Recommended treatments in order of protective effectiveness- - -
10、 - - - - - - - - - - - - 10 B. What is involved in galvanic corrosion- - - - 17 iii -“ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-889A 22 September 1969 MILITARY STANDARD DISSIMILAR METALS 1. SCOPE. 1.1 Purpose. This standard defines and
11、 classifies dissimilar metals, and establishes requirements for protecting coupled dissimilar metals, with attention directed to the anodic member of the couple, against corrosion. 1.1.1 Applicability. This standard is applicable to all military equipment parts, components and assemblies. 2. mFERENC
12、ED DOCUMENTS. 2.1 Issues of documents. The following documents of the issue in effect on date of invitation for bids or request.for proposal, form a part of this standard to the extent specified herein. SPECIFICATIONS MILITARY MIL-S-8802 Sealing Compound, Temperature-Resistant, Integral Fuel Tanks a
13、nd Fuel Cell Cavities, High Adhesion (Copies of specifications, standards, drawings, and publications required by contractors in connection with specific procurement functions should be obtained from the procuring activity or as directed by the contracting officer.) FSC MFFP Provided by IHSNot for R
14、esaleNo reproduction or networking permitted without license from IHS-,-,-3. DEFINITIONS. 3.1 Dissimilar metals. This standard terms metals dissimilar when two metal specimens are in contact or otherwise electrically connected to each other in a conductive solution and generate an electric current.
15、3.2 Galvanic corrosion. Galvanic corrosion manifests itself in the accelerated corrosion caused to the more active metal (anode) of a dissimilar metal couple in an electrolyte solution or medium, and decreased corrosive effects on the less active metal (cathode), as compared to the corrosion of the
16、individual metals, when not connected, in the same electrolyte environment. 3.3 Galvanic series. A galvanic series is a listing of metals and alloys based on their order and tendency to corrode independently, in a particular electrolyte solution or other environment. This tendency for dissolution or
17、 corrosion is related to the electrical potential of the metal in conductive medium. Galvanic corrosion is inherently affected by the relative position of the galvanic series of the metals constituting the couple. Metals closely positioned in the series will have electrical potentials nearer one ano
18、ther, whereas with greater divergence in position, greater differences in potential will prevail. Galvanic effects, i.e., corrosion of the anode will in the former condition be minimal, the latter condition will exhibit more signifi- cant corrosive effects. A galvanic series for corrosion structural
19、 metals, for sea water, is shown in Table II. Table I shall be used as a guide in determining the relative compatibility of dissimilar metal combinations. Compatibility does not indicate a complete freedom from galvanic action. 4. GENERAL STATEMENTS. (Not Applicable) 5. DETAILED REQUIREMENTS. 5.1 Mi
20、nimizing dissimilar metal corrosion. 5.1.1 When dissimilar metals are used in intimate contact, suitable protection against galvanic corrosion shall be applied. In some environments particularly with metals such as magnesium, steel, zinc, aluminum, in contact with copper, stainless steel, nickel, ga
21、lvanic corrosion may be appreciable. Consequently, care should be taken to protect the anodic member by proper electrical insulation of the joint or by excluding the electrolyte if this is feasible. 2 Supersedes page 2 of 7 July 1976 Provided by IHSNot for ResaleNo reproduction or networking permitt
22、ed without license from IHS-,-,-flI-STD- hence for each specific solution which is expected to be encountered for actual use, a different order or series will ensue. Galvanic series relationships are useful as a guide for selecting metals to be joined, will help the selection of metals having minima
23、l tendency to interact galvanically, or will indicate the need or degree of protection to be applied to lessen the expected potential interactions. Generally, the closer one metal is to another in the series, the more compatible they will be, i.e., the galvanic effects will be minimal; conversely, t
24、he farther one metal.is from another, the greater will be the effect. In a galvanic couple, the metal higher in the series represents the anode, and will corrode preferentially in the environment. 5.1.3 Metals widely separated in the galvanic series must be protected if they are to be joined. Approp
25、riate measures should be taken to avoid contact. This can be accomplished by applymg to the cathodic member a sacrificial metal coating having a potential similar to or near that of the anodic member; by sealing to insure that the faying surfaces are water-tight; by painting or coating all surfaces
26、to increase the resistance of electrical circuit. 5.1.4 A small anodic area relative to the cathodic area should be avoided. The same metal or more noble (cathodic) metals should be utilized for small fasteners, and bolts. The larger is the relative anode area, the lower the galvanic current density
27、 on the anode, the lesser the attack. The galvanic corrosion effect may be considered as inverse to the anode-cathode area ratio. 5.1.5 Metals exposed to sea water environments shall be corrosion and stress-corrosion resistant or shall be processed to resist corrosion and stress-corrosion. Irrespect
28、ive of the metals involved, all exposed edges should be sealed with a suitable sealant material conforming to MIL-S-8802. When non-compatible materials are joined, an interposing material compatible with each shall be used. 5.1.6 Materials other than true metals, i.e., non-metallic materials, which
29、must be joined to metals, should be considered as metallic materials, unless there is supporting evidence to the contrary. If these materials are essentially free of corrosive agents (salts), free of Supersedes page 3 of 7 July 1976. 3 Provided by IHSNot for ResaleNo reproduction or networking permi
30、tted without license from IHS-,-,-MIL-STD-887B CHG NOTICE 3 P 7 -I jt ,I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-889B 21 November 1979 TABLE II. Galvanic series of selected metals in Seawater. “- PER: Army Missile Command Report KS-TR
31、-67-11 , Practical Galvanic Series. Active (Anodic) Magnesium (Mg) Mg Alloy AZ-31B S MG Alloy HK-31A Zinc (hot-dip, die cast or plated) Beryllium (hot pressed) Aluminum (Al) 7072 cl. on 7075 Al alloy 2014-T3 Al alloy 1160-Hl4 Al alloy 7079-T6 Cadmium (plated) Uranium Al alloy 218 (die cast) Al alloy
32、 5052-0 Al alloy 5052-H12 Al alloy 5456-0, H353 Al alloy 5052-H32 Al alloy 1100-0 Al alloy 3003-H25 Al. alloy 6061-T6 Al a.lloy A360 (die cast) Al alloy 7075-T6 Al alloy 1160-Hl4 Al alloy 6061-0 Indium Al alloy 2014-0 Al alloy 2024-T4 Al alloy 5052-Hl6 Tin (plated) Stainless steel 430 (active) Lead
33、Steel 1010 Iron, cast Stainless steel 410 (active) Copper (plated, cast or wrought) Supersedes page 5 of 7 July 1976 Nickel (plated) Chromium (plated) Tantalum AM3 50 (active ) Stainless steel 310 (active) Stainless steel 301 (active) Stainless steel 304 (active) Stainless steel 430 (passive) Stainl
34、ess steel 410 (passive) Stainless steel 17-7 PH (active) Tungsten Niobium (Columbium) 1% Zr Brass, yellow, 268 Uranium 8% Mo. Brass, Naval, 464 Yellow brass Ivluntz metal 280 Brass (plated) Nickel-silver (18% Ni) Stainless steel 316L (active) Bronze 220 Copper 110 Red brass Stainless steel 347 (acti
35、ve) Molybdenum, Comm pure Copper-Nickel 715 Admiralty brass Stainless steel 202 (active) Bronze, Phosphor 534 (B-1) Monel 400 Stainless steel 201 (active) Carpenter 20 (active) Stainless steel 321 (active) Stainless steel 316 (active) Stainless steel 309 (passive) Stainless steel 17-7 PH (passive) S
36、ilicone Bronze 655 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-889B 21 November 1979 Stainless steel 304 (pass Stainless steel 301 (pass Stainless steel 321 (pass Stainless steel 201 (pass ive ) ive ) ive ) ive ) Stainless steel 286 ( d
37、esign metal couples so that the area of the cathode is smaller (appreciably) than the area of the anodic metal. For example, bolts or screws of stainless steel for fastening aluminum sheet, but not the reverse. Interpose a compatible metallic gasket or washer between the dissimilar metals prior to f
38、astening; or plate the cathodic member with a metal compatible to the anode. These are applicable to couples which are to serve as an electrical connection. b. Interpose a non-absorbing,inert gasketing material or washer be- tween the dissimilar materials prior to connecting them. This is applicable
39、 to couples which are not to serve as electrical conductors. 7 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-flIL-STD-BB7B NOTICE I GD W 77777II 0035300 5 W! MIL-STD-889B 7 July 1976 c. Seal all faying edges to preclude the entrance of liquids. d.
40、Apply corrosion-inhibiting pastes or compounds under heads of screws or bolts inserted into dissimilar metal surfaces whether or not the fasteners had been previously plated or otherwise treated. In some instances, it may be feasible to apply an organic coating to the faying surfaces prior to assemb
41、ly. This would be applicable to joints which are not required to be electrically conductive. e. Where practicable or where it will not interfere with the proposed use of the assembly, the external joint should be coated externally with an effective paint system. f. Welded or brazed dissimilar metal
42、assemblies should be coated with a paint system or other suitable protective coatings to at least 1/3 inch beyond the heat affected zone. g. In so called protective environments (usually referred to as humidity-controlled) cautlon should be applied to dissimilar metal combination treatments. If the
43、assumption is made that no corrosion will occur because humidity control will be maintained, the stringent requirements would be unnecessary. It must be recognized that humidity and moisture controlled environments can be assured only by hermetically sealed compartments or containers in which the mo
44、isture vapor content has been adequately reduced, so as to preclude condensation of water at the -lowest temperature expected to be encountered in the actual surface of the item. If humidity and condensate control cannot be maintained or is uncertain (frequently this is so) then dissimilar metal con
45、tacts should be treated as if protection were required against the worst en- vironment, 6. APPENDICES. 6.1 Appendix A. Lists priority protective treatments and systems for each metal or alloy. This listing should be consulted for the selection of systems to be applied in the joining of dissimilar me
46、tals. The sur- face finishes provided in the sublistings under each metal give the optimum first, and others in descending order of preference. Environ- mental conditions to which.the couple is expected to be subjected in service must be taken into account. Assurance should be established that lesse
47、r protective systems if selected, will fulfill the need. Consider- ations must be given to these factors: service conditions, electrical 8 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-PROJECT NUMBER: MFFP-0113 Provided by IHSNot for ResaleNo repro
48、duction or networking permitted without license from IHS-,-,-MIL-STD-889B 7 July 1976 APPENDIX A RECOMMENDED TREATMENTS IN ORDER OF PROTECTIVE EFFECTIVENESS 10. GENERAL 10.1 Scope. This appendix lists protective systems for each metal or alloy with optimum treatments listed first, and others in desc
49、ending order of preference. 10.2 Application. Each listing is presented as a guide only each application must be reviewed considering service conditions, design requirements and maintenance costs, 20, REFERENCE DOCUMENTS SPECIFICATIONS FEDERAL QQ-P-416 TT-C-490 Plating Cadmium Electrodeposited) Cleaning Method And
