1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.Copyright 2004 SAE InternationalAll rights reserved. No part of this publication may be
3、reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724
4、-776-0790Email: custsvcsae.orgSAE WEB ADDRESS: http:/www.sae.orgAEROSPACE RECOMMENDED PRACTICEARP1481REV.AIssued 1978-05Revised 1998-09Reaffirmed 2004-08Supersedes ARP1481Corrosion Control and Electrical Conductivity in Enclosure Design1. SCOPE:Corrosion control is always of concern to the designer
5、of electronic enclosures. The use of EMI gaskets to provide shielding often creates requirements that are in conflict with ideal corrosion control. This SAE Aerospace Recommended Practice (ARP) presents a compatibility table (see Figure 1) which has as its objective a listing of metallic couples tha
6、t are compatible from a corrosion aspect and which still maintain a low contact impedance.2. REFERENCES:2.1 Applicable Documents:The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other pub
7、lications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specifi
8、c exemption has been obtained.2.1.1 U.S. Government Publications: Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.MIL-M-3171 Magnesium Alloy, Processes for Corosion ProtectionMIL-C-5541B Chemical Conversion Coatings on Aluminum and Alum
9、inum Alloys - June 30, 1970MIL-C-81706 Chemical Conversion Materials for Coating Aluminum and Aluminum Alloys - June 30, 1970MIL-STD-889 Dissimilar MetalsSAE ARP1481 Revision A- 2 -FIGURE 1SAE ARP1481 Revision A- 3 -FIGURE 1 (Continued)SAE ARP1481 Revision A- 4 -2.2 Definitions:2.2.1 MIL-C-5541 CLAS
10、S 1A AND 3 - CHROMATE CONVERSION COATINGS: The military specification controls the engineering requirements of these coatings. Class 1A is intended as a base for painting, while Class 3 is a controlled surface resistivity. Chemical materials for applying the coatings are contained in the qualified p
11、arts list (QPL) of MIL-C-81706.2.2.2 CORROSION FREE COUPLE: A corrosion free couple is one that will maintain an impedance less than 2.5 m2at 1.4 kg/cm2(200 psi).2.2.3 TABLE SYMBOLS: The following is a more complete definition of the symbols used in the table:a. The couple is completely compatible a
12、nd will function without further care.b. Couple should be sealed only if exposed to salt environment.c. If the couple is exposed for over 10% of its life-time to atmospheres above 85% relative humidity (RH), the exposed edges of the couple should be sealed with sealing compound or primers. If expsou
13、res are less than 10% of the life at 85% RH, the couple may be considered as category B.d. The couple is compatible and will function without further care if the use environment is generally below 85% relative humidity (RH) and use temperature below 160 F (71 C). If exposure exceeds these limits, th
14、e couple should be sealed.e. Couple is sufficiently corrodible to require sealing at all times.f. Material is inherently corrodible and the corrosion product will cause loss of couple conductivity.2.2.4 EXPLANATIONS:2.2.4.1 Increase in Corrosion: This table is about dissimilar materials. Some materi
15、als, by themselves, will corrode in a given environment. If corrosion will not increase because of the presence of the other element, it is listed as acceptable in this table.2.2.4.2 Material Recommendations: It should be mentioned that the table in no way endorses the use of a specific material or
16、finish in shielding design beyond that which the inherent physical properties of the materials themselves merit.2.2.4.3 Use of Magnesium: It is recognized that magnesium is used in a number of applications. It is so corrodible that the only finish that has been found to be satisfactory is a minimum
17、of 1 mil tin plate or reflow tin. In completely controlled environments, MIL-M-3171 Type 3 chemical coatings may be used. However, the initial resistance will be higher than tin and may increase with time.SAE ARP1481 Revision A- 5 -3. BACKGROUND:The table of dissimilar materials has been developed t
18、hrough experience and testing in “use“ atmospheres. No attempt was made to measure half-cell voltages of materials nor was any attempt made to develop an electromotive force series. Each couple on the table has been used successfully in design as indicated by the code letter which will be further ex
19、plained. Successful usage means that each couple will remain, within measureable tolerance (10%), at the same electrical conductivity as the installed conductivity over long use periods. Corrosion which may occur will not degrade the couple structurally or electrically. MIL-STD-889 is designed to provide structural integrity. This table provides more restrictive control since corrosion will degrade electrical conductivity long before any structural damage occurs.PREPARED BY SAE COMMITTEE AE-4, ELECTROMAGNETIC COMPATIBILITY
