In message <[email protected]>, dated Fri, 31 Jul 2009, "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> writes:
>This is one of the items one uses and prescribes for > >years without actually KNOWING why. > >Today my recommendation of replacing > >a stainless steel bolt by a special > >M4 sized oxygen free ground bolt > >was challenged with the motiviation > >that copper may oxide and cause ?verdigris? > >(copper green) Copper does oxidize slowly in air, but the colour is normally brown. The green colour appears when there are acidic contaminants present, and since one that works is sodium chloride solution[1], which is everywhere, it is very common. The green stuff is not true 'verdigris', which is a copper acetate. [1] It's acidic in the sense that the copper removes the chloride ions >from the solution, which thus acts as an acid. I don't see any merit in oxygen-free copper, and stainless steel would be quite as effective and at least as reliable as a conductive fastening, especially in harsh atmospheres. Curiously, stainless steel is not widely used as an electrical conductor, but, granted that it has quite a high resistivity compared with copper, it is effective. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
