Using silicone grease on enclosure gaskets - Page 1
Forum section: electronics / projects

author: reagle
author_rank: Unknown
timestamp: September 19, 2016, 01:48:58 pm
content: I remember Dave mention this in a few videos- using silicone grease style lubricants on gaskets for products that are subject to immersion or water spray. How does that work in general? You'd think lubricant by itself is not able to keep water out, so is it the "unwetable" property of it that helps?

author: Paul Moir
author_rank: Frequent Contributor
timestamp: September 19, 2016, 03:29:52 pm
content: That and the fact that it's usually supplied quite thick. Note that some hydrocarbon grease bases are also pretty water soluble.As a testament to how hard it is to wash away, silicone grease is commonly used to lubricate plumbing valve stems & seals despite it being a pretty poor general lubricant.EDIT: Finally it's very compatible with rubbers and plastics, which is often what seals are made with.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 19, 2016, 04:03:28 pm
content: The silicone grease can fill small residual leaks, like scratches that are too small for the rubber ring to fill. So it is also used in vacuum applications, unless you need it very clean and have trouble with some of the grease evaporating.

author: reagle
author_rank: Unknown
timestamp: September 19, 2016, 04:09:35 pm
content: So is that a fairly standard practice in the industry?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: September 19, 2016, 04:42:14 pm
content: One thing to watch for: don't use it if the product will be in a factory that does painting. The silicone can get onto the part being sprayed, and it will resist adhesion of the paint material. This causes a flaw known as "fish eye".

author: Pjotr
author_rank: Frequent Contributor
timestamp: September 19, 2016, 05:10:44 pm
content: And don't use it with equipment with sensitive switches and low level relays. The silicon vapour leaves a very thin but highly insulating film at the contacts after time. That's why there is also silicon free thermal interface grease.

author: reagle
author_rank: Unknown
timestamp: September 19, 2016, 05:16:55 pm
content: That one may indeed be an issue in my design- I am using metal dome contacts on the board. They are held in place by sticky tape squares, but there is a "vent" via through the board.Also, what about various connectors, such as FPC, or even regular ones- does the film end up forming on them?

author: Paul Moir
author_rank: Frequent Contributor
timestamp: September 20, 2016, 02:33:24 am
content: I really doubt it will be an issue with those. The even make contact cleaner with the stuff in it:http://www.mgchemicals.com/products/cleaning-products-for-electronics/cleaners/contact-cleaners/contact-cleaner-with-silicones-404b

author: helius
author_rank: Super Contributor
timestamp: September 20, 2016, 03:09:15 am
content: Silicone is known as the "universal contaminant" in manufacturing and causes a host of problems by being so easily dispersed and so environmentally stable.http://www.cemag.us/article/2004/03/silicone-contamination-part-1However, none of those is likely to be an issue sealing gaskets for wet operational environments, as long as the silicones are never used where sensitive assemblies are manufactured.

author: promacjoe
author_rank: Regular Contributor
timestamp: September 20, 2016, 03:30:42 am
content: Another benefit of using silicone grease on rubber gaskets, it allows the gaskets to slide into the grooves easier. Less chance of the gasket getting bunched up, which might leave a hole in the seal. also, it makes the gasket less likely to have problems if the case is twisted or some force is put on it, that is out of the ordinary.Joe.

author: zapta
author_rank: Super Contributor
timestamp: September 20, 2016, 04:07:52 am
content: Quote from: reagle on September 19, 2016, 04:09:35 pmStandard practice for underwater equipment. And each time you open it, you clean the old gunky grease, replace the compressed O-ring, grease again all around the new O-ring and tighten in a balanced pattern. You need to match the grease type to the O-ring's material.

author: MatteoX
author_rank: Regular Contributor
timestamp: September 20, 2016, 04:14:54 am
content: Silicone might be OK for hobby electronics but its use in professional electronics(e.g. mil or space) is strictly controlled.Silicone is not easy to clean and it can migrate to significant distance.Silicone contamination of electrical contacts (e.g. relays and potentiometers) isa big issue.There are well known cases of enclosed relay contact contamination where siliconepassed throught the microcracks in packaging caused by wave soldering. Theseeffects show much later during the product lifecycle and cannot be detect in the initialproduct testing.Silicone also has negative impact during assembly (soldering, adhesive bonding,...)In space and military electronics use of silicone is strictly controlled and limited. Just anintersting example: NASA issued an alert regarding wristband silicone contamination (http://www.spaceref.com/news/viewsr.html?pid=16511).

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: September 20, 2016, 05:48:57 am
content: I use it to grease the O-rings that go between waveguide segments. Recommended to ensure a pressure seal, but doesn't really help the electrical conductivity (that requires the screws to be torqued properly).

author: LabSpokane
author_rank: Super Contributor
timestamp: September 20, 2016, 06:29:08 am
content: Quote from: radar_macgyver on September 20, 2016, 05:48:57 amVirtually ever coax connector over 1/4" I've used or seen used comes with a tube of silicone grease to lube the threads on the coupling and the rubber gasket. This is partially to prevent thread corrosion on the aluminum coupling and partially as a sealant (even though each connection is triple wrapped with WX proofing).Also, when ever I get a new motorcycle, the first thing I do is pull the electrical connectors and pack with silicone grease. It really helps prevent water intrusion problems in that application.So, silicone isn't always a negative when used in the right application.In the wrong application it's easy to see how silicone grease would be a nightmare from hell.

author: TheBay
author_rank: Unknown
timestamp: September 20, 2016, 12:12:16 pm
content: I use Vaseline "Petroleum Jelly", never had an issue with that and especially around anything electrical/electronic - I may be told otherwise however?I will not use anything Silicone related around metalwork or electronics, but I'm sure it's Silicone with anything acidic in it that causes an issue,I'm sure there must be Silicone products designed without this for these purposes.

author: Chris Jones
author_rank: Regular Contributor
timestamp: September 20, 2016, 02:19:20 pm
content: I have read that it is particularly troublesome if silicone vapour gets into realy contacts that spark, IIRC supposedly the silicone turns into some sort of insulating glass on the contacts.

author: helius
author_rank: Super Contributor
timestamp: September 20, 2016, 04:30:05 pm
content: Quote from: TheBay on September 20, 2016, 12:12:16 pmPetroleum jelly and silicone are completely different. Petroleum is much less heat- and chemical-resistant and may be damaging to rubber components.QuoteThat's a separate issue and only applies to siliconesealants, not at all tolubricantsor greases.RTV silicone sealants (like most glues) release vapors when curing, and the type that releases acetic acid can cause corrosion on sensitive surfaces.For use directly on electronics, acrylic or epoxy glues are more compatible than silicone types.

author: Gyro
author_rank: Super Contributor
timestamp: September 20, 2016, 05:50:37 pm
content: QuoteIt is however a very good water repellent and is benign with signal level contacts, in fact it makes a good contact oxidation protector. Protecting vehicle battery terminals against acid attack is another common application. Vaseline was used for many years for applications like sealing screw threads on lifejacket emergency lights intended for immersion in sea water. If the OP's need is water penetration protection then it may well be suitable.

author: reagle
author_rank: Unknown
timestamp: September 20, 2016, 06:13:04 pm
content: Yes, that's exactly the goal- trying to improve sealing of the case gasket in water spray situations. The problem is, the board inside does contain things like dome switches. How long would it take for silicone vapors to migrate from a case edge to inside something like that one the board? Are we talking years, tens of years or months?

author: ConKbot
author_rank: Super Contributor
timestamp: September 20, 2016, 11:35:53 pm
content: Quote from: LabSpokane on September 20, 2016, 06:29:08 amYep, definitely good for that. I used to do long term vehicle instrumentation. Outdoor connections that would be on for the span of the test would get heatshrink put over and a gob of RTV shot into either end. Not that bad to remove surprisingly. But temporary connections (trailer etc) would get the connector fully packed with silicone dielectric grease, and the connection zip tied to the hitch to make sure the driver wouldn't forget to unhook them. Worked great for making cheap, robust, unsealed connectors (amp CPC) work good outdoors.