Help: What is the coating material on PCB in washing machine

Discussion in 'General Electronics Chat' started by santosh742598, Jul 14, 2013.

  1. santosh742598

    Thread Starter New Member

    Jul 14, 2013
    Today my whirlpool washing machine stopped working and on close inspection I found a 4.7 μF capacitor had ruptured. As the washing machine was not under warranty I tried to repair it myself but I found a gel type substance on both side of the pcb covering the component and soldering poing.
    The material was some kind of gel and I removed it. Now I have replace the capacitor and want to put the gel again as it might be working as humidity resistant element inside the washing machine.
    Can anybody inform me the material used in the process. the characterstic of the material as per my knowledge should be non corrosive, non conductive and gelly.
    Any help is appriciated.I require it urgently as otherwise I feel it may corrode the pcb.
    Thanxs in advance.:)
  2. MrChips


    Oct 2, 2009
    It is called conformal coating and is available in a spray can at electronics supply stores.
  3. Duane P Wetick

    Active Member

    Apr 23, 2009
    Several compounds are available to provide waterproofing pcb's. Dow-Corning make a clear rubbery (to feel) conformal coating and a commercial product called Humiseal is available. Some plastics used in IC production are hygroscopic (absorb water) degrading the chip. Applying a conformal coating after baking the PCB can restore the chip's performance.

    Cheers, DPW [Everything has limitations...and I hate limitations.]
  4. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    I am not an expert but what about using liquid electrical tape or lacquer ??
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
    Clear urethane spray is what I used to use. Humiseal is good but pricey. For specific repair areas I used clear fingernail polish (which is urethane)
  6. LDC3

    Active Member

    Apr 27, 2013
    To be specific, fingernail polish is not a polyurethane. But not all fingernail polish has a high impedance since it contains iron oxide (or other metals) for coloring.
  7. debe

    Well-Known Member

    Sep 21, 2010
    Not if you use clear varnish.
  8. monster_catfish

    Active Member

    Mar 17, 2011
    One of the more ingenious PCB insulating materials I know of was utilized in a company where I once worked in Orange County, California, for protecting circuit boards intended for emergency egress lighting systems fitted to the doorways of military helicopters.

    Called potting compound, this material comprised a two-part binary reagent that when combined in a container fitted around the PCB, would in seconds congeal to a rubbery consistency that completely encased the PCB in a perfectly water-proof seal that could survive prolonged immersion in salt water, with no adverse effect on the PCB functionality.

    That technique was in use many moons ago, so I imagine there are more easily applied and effective sealants in current use today, when total water-proofing is required for PCBs.
  9. bountyhunter

    Well-Known Member

    Sep 7, 2009
    As I said:

    CLEAR fingernail polish....

    that contains nothing for coloring