Looking for some feedback on bonding various parts of a painted metal chassis together for safety and EMC performance issues. I know we have a lot of experts out there on this topic and can remember a number of threads on the topic. Please help me pull it together: a.. When screwing the cover on the base will star washers cut through paint, even epoxy paint and provide a reliable connection? b.. Are there special versions of electrical star washers that work better than others? c.. What about oxidation of the mating surface? I understand star washers can make a gas tight seal. d.. Should there be a special treatment to the painted area where the screw/washer come together? e.. Do PEM nuts act as a good mating mechanism for the screw? There are many types are some better than others? What about the self clenching types? f.. One can get screws with captive washers. Are there any issues with these? Preferred Vendors and types? g.. There are various chemical materials to keep screws from backing out and are applied to the threads of a screw such as those from Loctite. Do these interfere or help? Are some formulas better than others? h.. Under the paint if the base metal is steel are there any treatments or plating that help? For Steel, for Aluminum? i.. If the chassis is plated steel instead like zinc chromate yellow. What changes? j.. Proper plating on screw and star washer? (assume painted steel) Any advice on the topic welcome! Thanks in advance!
Chris Wells Senior Design Engineer Cutler-Hammer [email protected]
