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Thread: Silicon Grease to Moisture Proof Fluorescent Light

  1. #1
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    Default Silicon Grease to Moisture Proof Fluorescent Light

    I have moisture proofed many lights and electrical items (cars, exterior, etc.) by using silicon grease (the type sold for waterproofing auto ignition systems) with good success.

    But, I wanted to see if anyone had done this with normal 8 foot fluorescent (one and two pin type lamps) fixtures.

    At the pool where my daughter swims it is very humid and I jiggled the bulbs to get them working again (typical open commercial fixture), and I wanted to see if anyone has had any problems with silicon (or other better suggestions) to help the fixtures last longer. Any problems with silicon causing the plastic in the fixture to fail?

    Also, has anyone tried this in a typical exterior PAR fixture with 70-150 watt floods...

    -Bill

  2. #2
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    Default Re: Silicon Grease to Moisture Proof Fluorescent Light

    Well,

    Just an FYI... I did try Silicone grease on the ends of several single pin dual tube florescent light fixtures and I found out last night that the plastic spring ends that hold the light had completely disintegrated.

    So, even though I used grease specifically labeled for use in light sockets (to keep screw base bulbs from seizing), do not use silicone grease in or around plastic unless it is specifically recommended (like a flashlight "O" ring)."

    I will now have to replace the several fixtures I tried it on.

    -Bill

  3. #3
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    Default Re: Silicon Grease to Moisture Proof Fluorescent Light

    Hello Bill,

    Are you sure? That sounds really strange to me.

    I thought silicone grease was mostly inert. I have used it on a number of plastic parts with no problems, but never fluorescent lights.

    I'm scratching my head...

    Tom

  4. #4

    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    I'm fairly sure this has nothing to do with the use of silicone grease.
    Number one cause of this is heat. Number two is UV which is also why the diffusers yellow and get brittle.
    I've replaced a large number of sockets that I'm sure never saw silicone grease.
    However, I would not use any silicone grease made for spray on use since these contain a large amount of solvents. Either that made for plumbing or high vacuum (lab glassware) wiped on in a very thin amount. I've used these for outdoor lamps for decades.

  5. #5
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    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    Absolutely 100% sure that the grease caused the problem.

    1. I had inspected both fixtures (~5-8 years old) for problems back around beginning of February and everything was OK--other than some slight metal corrosion that I was trying to stop with the liberal application of silicone grease.

    2. I have now had two tubes of silicone grease with plastic caps (one from Radio Shack and another from Permatex Dielectric Tune-Up Grease p/n 20058) that both had the plastic caps fail (very top popped off at the first tread) fail after the metal tube seals had been punctured and the caps exposed to the silicone--after about 1+ years.

    My experience with the silicone grease plastic caps failing was why I first posted the question as it gave me a nagging fear that this was not a one-off failure.

    I have looked on the web for any reports of this type of failure--and I have yet to find any... That is why I posted my experience.

    Anyone out there have similar problems?

    -Bill

  6. #6

    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    I sorry but I would complete discount #2. I have seen this failure on all types of products. They use thin cheap plastic on most of these. The only one that I can think of where the product inside the tube might be expected to be unused in more than a year is artist paint.

  7. #7
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    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    I have tubes of grease, high-temp grease, white lithium, etc. from Permatex and others, that are many years old (some over twenty years old) and I have yet to see one of those caps fail (other than being glued on by gasket adhesives and such).

    I will admit that I have yet to find anything anywhere on the web using Google that speaks of plastic failures around silicone grease (other than silicone O-rings that should use fluorosilicone grease such as Molycote FS1292 per a camera web site).

    I don't know if it was the heat plus silicone grease or what that caused the light fixture's plastic to swell and crumble, but that was the only work done on the fixtures for years.

    The only thing I have found so far is Silicone based lubes may remove plasticizers in Nitrile O-rings. I am wondering if the silicone does not try and insert itself into the plastic and replace the plasticizers... Also there was a warning on one Silicone data sheet to not use the grease in the presence of chlorine--this may be a problem in an indoor swimming pool.

    Anyway, I am tempted to contact Dow Corning and ask them as I have no other explanation for what happened to the light fixtures.

    -Bill

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    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    Hello Bill,

    Yes, please contact Dow and get their read on this.

    I have not heard of the warning concerning chlorine. There may be a reaction going on.

    I am still scratching my head...

    Tom

  9. #9
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    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    Hi Guys,

    I finally got a chance to pull the old lights down from the ceiling and see what happened. There were two light fixtures, apparently of the same make, model and age/batch. I applied the same silicone grease to both fixtures at the same time and they all are on the same circuit.

    One fixture showed no problems with the plastic lamp holders.

    The other fixtures, one pair of holders (the "spring loaded" end on a single pin florescent lamp) looked (and slightly smelled) charred.

    The only physical difference I could see was there was the lamp holder springs where rusty on the failed fixture and OK on the good fixture.

    I am not sure if there was arcing and/or heating because of the rust or if the rust acted as a catalyst with the silicone (no proof of this) to char the plastic.

    So... my conclusion for now is that in a good fixture and after three months of use (four per night, 5-7 days per week) the silicone grease did not cause the plastic lamp holders to degrade (I used a pair of pliers to crush test various plastic parts to check their strength).

    -Bill

  10. #10

    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    Thanks for letting us know! I would have been surprised if the silicone had caused the problem, unless it had been a spray on (which uses a solvent).

  11. #11
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    Default Re: Silicon Grease to Moisture Proof Fluorescent L

    Hello Bill,

    Thanks for continuing to pursue this. I agree that silicone should not be the problem.

    Tom

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