If you're worried about galvanic corrosion. An excellent (and free) source of information is the Instrument Specialties Catalog and Design Guide. The back cover is a foldout which has a very nice color coded chart that shows metal compatibility while taking into account the environment.
Their graph is easily worth a thousand words. Chris > -----Original Message----- > From: Robert Wilson [SMTP:robert_wil...@tirsys.com] > Sent: Friday, March 01, 2002 12:20 PM > To: emc-p...@majordomo.ieee.org > Subject: RE: Pencil erasers for pre-EMI cleaning? (cleaning > mating surfaces, chassis, ) > > > One must take care to separate fact from opinions. "Mixing metals" as > you mention is NOT necessarily a sure way to promote corrosion. Yes, > steel against aluminum us not good practice since they are far enough > apart on the electromotive series that they will act as a local > battery > (in the presence of an electrolyte such as salt water), and the > aluminum > will corrode. Another bad pair is aluminum against copper alloys. > > But in a dry environment, no problem can occur since no moisture is > present. Galvanic corrosion without the presence of an electrolyte is > impossible. Other metal combinations are also problematic such as > aluminum against zinc plated or galvanized steel (or zinc plated > anything). Cadmium plated steel against aluminum is generally > considered > an acceptable combination, as is 300-series stainless steel against > most > metals. 300-series stainless (especially type 316) is considered > relatively "passive". > > One must simply choose the metal pairs carefully, taking into account > the environment, and if necessary making sure they are sufficiently > "close" in voltage potential to each other on the electromotive scale. > > Bob Wilson > TIR Systems Ltd. > Vancouver. > > -----Original Message----- > From: Wan Juang Foo [mailto:f...@np.edu.sg] > Sent: February 28, 2002 11:12 PM > To: emc-p...@majordomo.ieee.org > Subject: RE: Pencil erasers for pre-EMI cleaning? (cleaning mating > surfaces, chassis, ) > > > > David, > You mention that you have a Steel and Aluminium to content with. My > opinion about mixing metal parts in an assembly (chassis) is a sure > way > of > promoting corrosion, especially if the installation is in a humid > environment. If you want the chassis to be a reliable electrostatic > shield > do not have panels that are made with different metal bolted to the > 'frame' > or chassis. Under some codes this is a 'No Go' area. > > BTW, I assume that you must be working with a small box, otherwise you > would need much more than a 'rubber eraser' to clean the mating > surfaces. > > All equipment metalwork should be electrically bonded in a manner > which > does not rely on 'hopeful' electrical conduction through > anti-corrosive > treatment like anodised aluminium and paint. Careful attention to the > assembly process will weed out things like ball-bearings races, nylon > runners and coasters, or other insulating materials. > > Conduction through painted panels should not be dependent on the > gripping > action of star washers. The design should be such that no currents > flows > in any part of the metal work. The objective is to ensure that any > part > of > the metalwork can be relied upon as an effective electrostatic screen > and > not the reverse, a radiator. > > Tim Foo > > > > ------------------------------------------- > 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...@mediaone.net > > 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...@mediaone.net 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"
