Silicon grease

[pugwash]

A small item in PB or YM recently said it's better to use silicon grease than vaseline for protecting electric contacts because it'smore endurable. I'm about to treat my masthead and thru-deck fittings. Spay-on grease would get deeper into the crevices but solid grease could be caked on more thickly. Which do you think is better? Am I doing the right thing?

 

[Guest]

The solvents in some of the spray on type lubricants can actually remove any protective grease that was there in the first place. The intention is to cover the metal with a film that will exclude oxygen and moisture to preserve the surface. In the process, however, you make the surface sticky and airborn contaminants will now stick to it and cause corrosion. My choice would be a light coat of silicone grease on the mating surfaces but try to avoid exposed surfaces.

tech@yandina.com

 

[pugwash]

Sounds like good advice, but is it still better than Vaseline?

 

[Guest]

As an old salty seadog .... 'thick' greasing of moving parts on a seagoing craft is not the way .... particles and other matter get held in the grease ... its better to oil than grease.

But your problem is that the mast fittings will be out of sight and each for extended period ...... so only enough to do the job and not lay it on thick !
Choice of grease is I consider not that critical and any good quality silicon or vaseline should do it ....

 

[johnt]

well..its a lot more expensive if nothing else..personally I use ptfe spray or wd 40, it aint sticky and it dont collect grit...but it needs doing annually

 

[philip_stevens]

I wouldn't dare use WD40 on anything other than bare metal. When I was in the Fleet Air Arm, they started using it on units in the electronic and radio bays of helicopters. It was soon discontinued when it was found to cause more problems than it got rid of.

The reason?? After appilcation it loses its solvent and becomes sticky. The helo hovered over ground and blew up dust that stuck to the WD40. When it went over the sea and hovered, it picked up spray that stuck to the sticky WD40 - and back to problems of insulation or lack of it.

After this, it was only used to wash the skin of the helo, and seal up any cracks in the skin.

So be aware of its limitations if you go to use it on electrics.

On electrics, a spray grease or silicone is better. It is not sticky when the solvent evaporates.

As an electrician (25yrs) in the MN, I have had first hand knowledge of WD40.

regards,
Philip

 

[stuartw]

Please, please please-Do not use silicone grease!

I sell contact lubrication for a living, so I cannot advertise, but please believe me, silicone grease is the worst thing to put on an electrical contact.
Silicone grease under, certain conditions can break down to produce silicon carbide which is an insulator. This effectively renders the contact useless. Whereas silicone grease is very good at keeping water out, it will ultimately increase the contact resistance.
Specialy formulated contact lubrication (oils & greases) contain anti-oxidants to keep contacts free of oxide build up, and actually reduce the contact resistance.
Aerosol versions, contain cleaning solvents, which when evaporated, will leave a film of oil or grease on the contacts. Contact grease should be applied to mating terminal parts, then-and only then- could silicone or a waterproof grease be applied on the outside to prevent moisture ingress, to improve weather resistance.
Just to underline the very bad effect of silicone - electric trains have been brought to a standstill due to 'Mr. Sheen', a very evasive silicone polish.
RS components, Farnell and Maplin sell various greases and oils especially for contact lubrication and protection.

 

[Guest]

Re: Please, please please-Do not use silicone grease!

Curious, under what conditions is Silicon Carbide formed?

At one time it was practice in the aircraft industry when making off Aluminium cables to use silicon grease in the terminal bucket to ensure exclusion of moisture from the crimped joint, a practice which I use and recommend to this day for making of any cable in the marine environment. I have had no problems (thus far) with anyof my cables developing high resistance joints.

 

[philip_stevens]

Re: Please, please please-Do not use silicone grease!

Stuart,
thanks for explaining the more obscure properties of silicone. I was aware of its insulation properties,i.e. its dielectric strength, but I thought the original posting was about sealing the contacts, and I took that to mean plugs and sockets etc, and to prevent the ingress of moisture. If I misread the thread, my apologies.

I use CRC aerosol silicone and spray grease on connecting plugs and sockets, and have never had any problems of increasing resistance.

regards,
Philip<P ID="edit"><FONT SIZE=-1>Edited by philip_stevens on Sun Jun 10 22:56:44 2001 (server time).</FONT></P>

 

[stuartw]

Re: Please, please please-Do not use silicone grease!

Basically under arcing conditions- a spark will break down the air, and the silicone will combine with atmosheric carbon dioxide.
It is not a crimped connection that is the problem, as that is done uner dry clean conditions. Silicone oils contained in the grease can migrate and ultimately get on the actual mating contact of the connector itelf. It is customary practice THESE days to fill the back shell of a connector, ie the crimped area with a potting medium, eg a flexible two part polyurethane, which prevents moisture ingress and provides additional strain relief. Low current, ie sensors etc, will of course present little problem. Larger currents, where a high resistance joint may develop, the silicone oil in the grease can dissociate even under micro arcing conditions, particularly under vibration conditions- eg and aircaft.

 

[Guest]

I can only agree with this guy about WD40 .... seeing various articles on ship stop working after using it ... and also when I raced cars many years ago .... I was told as driver / owner by the mechanics NEVER EVER spray the ignition of the car ... you get build up of residue and soon no 'spark' .... its true, I 'knew' better and sure enough points and distributor failed. I used it like most to stop water in the ignition ... I actually ended up stopping the electrons !!!!