Appropriate use of Dielectric Greases

[ELA]

Q) Would you consider it an ?appropriate use?, to apply a ?Dielectric Grease? between two electrical mating surfaces?

I recently read assembly instructions for a cable with a butt splice that instructed assemblers to apply a dielectric grease on each wire surface prior to crimping a butt splice.
My first thoughts were that this would be a bad thing, thinking strictly from the theory of a dielectric.

I did a bit of searching on the net and found lots of opinions both favoring the use of dielectric grease on electrical connections as well as some who were adamantly against its use, directly on electrical connection points.

I was interested in hearing your opinions, or better yet your direct experiences, with dielectric grease use.

I believe we all could agree with its use around or over electrical connection points once made, to prevent the intrusion of moisture and to help prevent corrosion.
This poll is meant to address its application to conductive surfaces prior to mating.

 

[ELA]

Follow up

Follow up

With respect to a crimped connection I have come to feel that using the dielectric grease should be acceptable since a good crimp connection is supposed to be a ?gas tight? one. This says to me that any dielectric grease would be displaced from between the conducting surfaces during the crimp process. Thus the remaining grease would fill in voids around the conductors and be beneficial in protecting the joint against moisture.

I know there are lots of different kinds crease including noalox that are more or less conductive. I am also aware of the old school use of Vaseline on light bulb sockets.

I am mostly interested in opinions of true dielectric greases, often referred to as ?Marine Grease?. Often used in marine applications as well as automotive to hold off the intrusion of moisture in electrical connections. Most of what I have read indicated great success with its use.

I do not have a lot of direct experience with its use. It seems to me at this point that it is probably very beneficial as long as the electrical connection is a good one to begin with. It also seems like it has the potential to make a marginal connection even worse.

Here is an interesting product I found while researching this that I had never heard of before:
http://www.stabilant.com/appnt20h.htm

Your opinions/experiences please?

 

[LJSMITH1]

Yes. Dielectric grease is neither conductive or insulative. It is specifically formulated to lubricate and protect electrical connections from corrosion that will ultimately cause higher contact resistance.

Permatex/Loctite and others make greases specifically for this purpose.

https://tds.us.henkel.com//NA/UT/HNAUTTDS.nsf/web/E7D49FEC1C1903B6882571870000D946/$File/DIEG-EN.pdf

Ordinary greases are not the same, and could actually be conductive or cause corrosion.

I have used dielectric greases in the manufacture of MIL-SPEC snap-action switches for high current and low current application. The performance is unmatched and can significantly extend the life of mechanical, electrically-conductive assemblies, as well as provide a very effective corrosion/tarnish barrier for contact surfaces.

The only area that I would be concerned with is the use in assemblies that have a lot of heat (i.e. very high current conditions, arcing contacts, high ambient temps, etc.) The grease has a tendency to lower its viscosity at elevated temps, or could completely evaporate if temps are high enough. However, for most applications, this is not the case and the grease works very well.

That's my $.02

 

[tkb]

I use the Dielectric grease on my flat 4 wire trailer hitch plug when it is not in use.
It keeps the dirt and corrosion out of the pin connector.

 

[don_resqcapt19]

Yes. Dielectric grease is neither conductive or insulative. ...

How is that physically possible...it has to be one or the other. From many common applications of dielectric grease (protection of connectors from corrosion for example) it has to be non-conductive, otherwise it would short out the adjacent pins on the connector.

The link you posted shows a dielectric strength of 19.8 kV/mm....air has a dielectric strength of about 3 kV/mm...that sure looks like an insulator to me. Even the description indicates it is an insulator.

The compound prevents voltage leakage around any electrical connector thereby insuring a strong spark in high energy ignition systems.

 

[LJSMITH1]

How is that physically possible...it has to be one or the other. From many common applications of dielectric grease (protection of connectors from corrosion for example) it has to be non-conductive, otherwise it would short out the adjacent pins on the connector.

The link you posted shows a dielectric strength of 19.8 kV/mm....air has a dielectric strength of about 3 kV/mm...that sure looks like an insulator to me. Even the description indicates it is an insulator.

Sorry, perhaps I should have explained a bit better. The specific formulation of dielectric grease allows for many typical mechanical electrical connections to 'penetrate through' the grease down to the base metal connection. The areas around the point connections are sealed off from atmosphere to prohibit corrosion or tarnishing that would otherwise eventually increase the contact resistance. This formulation also will not harm many plastics or rubber compounds as well as tarnish platings like tin, silver, or copper.

While the base grease is an insulator by itself (i.e. if sandwiched between two conductive plates), it is not 'permanent' enough to get in the way of contact mating surfaces with high mechanical contact forces and small surface areas - such as pin/socket contacts, knife contacts, blade contacts, setscrew contact, etc.).

While you would use Dielectric Grease on relay pin contacts, you would not use it on the actual relay contact surfaces (due to potential arcing or large contact surfaces with low contact pressure).

I hope that clarifies my statement a bit more.

 

[zog]

You want to use a conductive grease between mated conductive surfaces. NO-OX-ID is the most widely used.

I just had a similar thread on this, easier to link to thread than re-hash it all here.

http://www.eng-tips.com/viewthread.cfm?qid=260927&page=4

 

[LJSMITH1]

You want to use a conductive grease between mated conductive surfaces. NO-OX-ID is the most widely used.

I just had a similar thread on this, easier to link to thread than re-hash it all here.

http://www.eng-tips.com/viewthread.cfm?qid=260927&page=4

I believe the OP was talking about a crimped butt splice (i.e. high mechanical point force, small contact areas).

Q) Would you consider it an “appropriate use”, to apply a “Dielectric Grease” between two electrical mating surfaces?

I recently read assembly instructions for a cable with a butt splice that instructed assemblers to apply a dielectric grease on each wire surface prior to crimping a butt splice.

If you are looking at a lap joint on a busbar, or some other similar construction (i.e. large surface area, low contact force), then any filled conductive grease would be good (i.e. copper filled, silver filled, aluminum filled, etc.). However, use of this grease must take into account any surrounding incompatible materials (i.e. rubber, plastic, etc.) and high temperature conditions (i.e. arcing, ambient temps, etc.).

 

[ELA]

Thanks for the replies.
I think subject is a complicated one since there are many variables involved.
As I stated I am feeling ok with the "dielectric compound" in a crimp joint since a good crimp is a gas-tight joint.
I do not feel so good about using it on a lap joint.
Is it really good to use it on an electrical connector pin or compression type connection as so many marine applications seem to advocate?

It seems to me that it is dependent upon how tight the joint is.

I understand the use of a conductive compound on a isolated joint where leakage between conductors is not a consideration, but that is not what I wanted to discuss here.

 

[LJSMITH1]

Thanks for the replies.
I think subject is a complicated one since there are many variables involved.
As I stated I am feeling ok with the "dielectric compound" in a crimp joint since a good crimp is a gas-tight joint.
I do not feel so good about using it on a lap joint.
Is it really good to use it on an electrical connector pin or compression type connection as so many marine applications seem to advocate?

It seems to me that it is dependent upon how tight the joint is.

I understand the use of a conductive compound on a isolated joint where leakage between conductors is not a consideration, but that is not what I wanted to discuss here.

As an engineer, and someone that has worked for an electrical connector and switch manufacturer (and as a Marine Mechanic), I can tell you that one type of grease cannot be used for all applications. Both types have their respective applications.

Standard, translucent dielectric grease is widely used in automotive connectors, marine electronics, or other applications where moisture and corrosion on mechanical contacts would adversely affect contact resistance. The other factor is the type of connection and how close the other connections are.

A gas tight, static, and mechanically sound electrical connection technically would not need any grease. The primary purpose of the grease is to prevent oxidation and to lubricate.

Gold plated contacts, which do not corrode and have a very low contact resistance, have limited wear resistance. However, gold plating is also not practical for many applications, and some lubricant may still be needed to reduce wear on the contact surfaces. In this case, dielectric grease would be an option.

However, dielectric greases will not technically "improve conductivity" as they do not add contact area or contact pressure to the basic contact joint. This is where conductive filled greases come into play. The conductive grease technically adds to contact area, and also can lubricate moving parts as well. The result may be a lower contact resistance, but not necessarily resulting in a higher current carrying capability.

With regards to a lap joint on a busbar, a conductive grease or anti-oxidant would be the best choice. Same thing goes for an aluminum setscrew lug. However, you would not use conductive greases in applications where the adjoining contacts are close enough for excess grease to cause 'bridging' between circuits (especially low voltage & current applications <1V & <10mV).

In an application of a crimped butt joint on a single conductor, application of either grease would suffice and not cause any issues - as long as the compounds don't affect the insulation near the joint.

Contact resistance is basically a function of contact surface area, contact point pressure, metal conductivity, and cleanliness. The more contact area and pressure provided, combined with increased contact cross-sectional area, will allow more current to pass without heating up the contact area.

 

[weressl]

Q) Would you consider it an ?appropriate use?, to apply a ?Dielectric Grease? between two electrical mating surfaces?

I recently read assembly instructions for a cable with a butt splice that instructed assemblers to apply a dielectric grease on each wire surface prior to crimping a butt splice.
My first thoughts were that this would be a bad thing, thinking strictly from the theory of a dielectric.

I did a bit of searching on the net and found lots of opinions both favoring the use of dielectric grease on electrical connections as well as some who were adamantly against its use, directly on electrical connection points.

I was interested in hearing your opinions, or better yet your direct experiences, with dielectric grease use.

I believe we all could agree with its use around or over electrical connection points once made, to prevent the intrusion of moisture and to help prevent corrosion.
This poll is meant to address its application to conductive surfaces prior to mating.

Dielectric, as a term, refers to an insulating compound, as in capacitors there is a dielectric compound, layer, foil between the electrodes.

A connection may be coated with a lubricant in the case of moving contact to prevent it from seizing and welding. The conductive qualities of that compound would be unimportant, it could be either high or low as the compound's function is lubrication, not conduction. The connecting surfaces must have sufficient wiping action to actually clear the compound away from the actual conducting surfaces.

(I think it is needless to say that any greaselike compound will be less conductive than solid metal.)

A stationary connection may be coated to prevent the contact surfaces' corrosion. The conductive properties would be immaterial to the primary function of the compound in this case as well.