Steel, nickel, and zinc are all relatively poor conductors, at least as compared to copper or aluminum. Of these, the best conductor is zinc. But in your application the type of metal to use as plating is clearly irrelevant, since the plating will carry very little current. Almost all of the current will flow in the metal substrate (steel or stainless steel), even taking skin depth into account (at any reasonable frequency you are liable to be shielding against).
Low-300 series stainless steels (301, 302, 304, etc) are poor electrical conductors (and a really lousy thermal ones as well). The higher-300s series (316, 317, etc) are even worse. Their conductivity is many times worse than steel. But that may make little difference anyway in your application. As far as what finish is recommended on stainless, the answer is generally "none". The passivated finish as supplied in the original sheet is all that is usually used. In any event, passivation or no passivation is entirely irrelevant to conductivity, since the "passivation" is simply a molecules-thick oxide layer that is too thin to have an effect on the electrical parameters. On that note, if you zinc plate, you MUST passivate after plating, or risk the typical white zinc corrosion products that result from exposure to humidity. Usually a chromate conversion coating is used for this purpose and this also makes an excellent paint base (to which the paint adheres very well). Painting nickel or chrome plate is not recommended since paint adheres poorly (especially to chrome plate), but there is no particular electrical reason why you would want to plate these metals anyway. Bob Wilson TIR Systems Ltd. Vancouver. -----Original Message----- From: Sam Jayashankar [mailto:sam.jayashan...@sanmina-sci.com] Sent: May 29, 2002 10:27 AM To: EMC PSTC (E-mail) Subject: Conductive Coating Hi All, I have some queries regarding conductive coating for an enclosure design I am currently reviewing. The enclosure material is made of steel. The coating specified by the packaging/mechanical team is Zinc plate per ASTM B633, Type III, Class FE/ZN 5. How conductive is this Zinc plating? Does Nickel or Chromium plating offer better conductivity? The mechanical team is also looking into using stainless steel (passivate per SAE AMS QQ-P-35) for the enclosure doors. What is the recommended finish/coating for stainless steel? Thanks in advance for all help rendered. Regards, Sam Jayashankar EMC Engineer SANMINA-SCI 6751 - 9 Street N.E. Calgary, AB T2E 8R9 Phone: (403) 295-5124 Cell: (403) 875-1292 Fax: (403) 295-8862 E-mail: sam.jayashan...@sanmina-sci.com ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
