to coat, or not to coat, that is The Question

Discussion in 'The Projects Forum' started by cosmicsunset, Oct 26, 2013.

  1. cosmicsunset

    Thread Starter New Member

    Oct 24, 2013
    I just repaired the engine control module from my 1991 pickup truck. It had a faulty electrolytic capacitor that leaked electrolyte and corroded a portion of the board despite it having a thin conformal coating. There was also an area on the opposite side of the board that was very slightly corroded but it appeared unrelated and likely from moisture that was sealed in during coating at the factory.

    Anyway, after scrubbing like an archeologist for two days I finally got the board clean, the capacitor replaced and all remaining electrolyte neutralized with baking soda and rinsed away with cold water. I dried the board with compressed air and now it's sealed in a static shielding bag along with two huge packets of desiccant and some anti-static pink plastic between the board and desiccant (no idea if they're static safe).

    Obviously doing all this work required removing the conformal coating from several areas of the board. I'm trying to determine if I want to repair the coating and if so what material to use.

    The board will be installed in a vented metal box inside the plastic "kick panel" located in the cab of the truck beside the passenger's feet. So, it's not exactly a corrosive location. The board was mainly corroded by the electrolyte, not humidity or vapors or anything like that, so I'm thinking maybe it would be fine to not bother patching the coating in those areas and just reinstall the board.

    I also thought about sealing up the metal enclosure with silicone caulking or gasket maker since I already have both of those here and wouldn't need to find a coating material. However, I really don't want to have to repair this thing ever again, so maybe it would pay to track down and purchase a coating product that I can put over the repaired areas.

    Do you think I should repair the coating?

    And, if yes, where in the world can I find a suitable product locally? I'd rather not wait for an order from an online retailer but according to their websites neither Radio Shack or Home Depot have conformal coating materials, tho I suspect there are suitable products being sold for other purposes, like maybe the polyurethane sealants in the paint section.

    Thanks in advance for any advice you can offer
  2. MaxHeadRoom


    Jul 18, 2013
    There is Glyptal that is an electrical sealant, but it is not clear like Conformal coating.
    Any electrical wholesaler or supplier should stock it.
  3. cosmicsunset

    Thread Starter New Member

    Oct 24, 2013
    unfortunately I live in a pretty small town and since my truck won't run without this controller I'm limited to bicycling distance right now.

    I do have a can of that plasti-dip stuff from home depot. It's the spray on rubber coating for tool handles and things like that. It says it's electrically insulating so I guess that would work too, like the Glyptal, and the only disadvantage would be that if there was a leak somewhere and corrosion began under the opaque coating it wouldn't be visible.

    I also have a can of clear enamel spray paint but it says it contains xylene and toluene so I'm concerned it could harm the board. That seems like it might be a good option though if I can be sure it won't do any damage. Has anyone tried that before?
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
  5. cosmicsunset

    Thread Starter New Member

    Oct 24, 2013
    Cool. I will go ahead and give it a try with the clear coat I have (image attached). If a basically identical product has worked for you then I have a lot more confidence this will be ok but I think I'm still going to test a small area first and stick to thin coats because there are so many solvents listed in the ingredients.

  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    I would be more worried you'll spray paint into a connector then condensation on a board mounted inside the truck. But if it puts your mind at ease and you feel confident then have at it.

    This past July I had to put my '89 Dakota pickup to rest. Nothing better then an old pickup I say.
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Definately do not use a standard clear/white silicone. The acetic acid emitted from most silicones during curing will cause corrosion. Look for a "metal safe" silicone - intended for sealing steel windows and doors. Otherwise, use a clear polyurethane or acrylic. Krylon is good because it uses more volatile solvents that dry very fast and will be less likely to dissolve the bnd between board and copper. The fiberglass board is fairly inert to solvents (acetone, alcohols and hydrocarbon solvents).