Dielectric grease is a non-conductive, silicone grease designed to seal out moisture and, therefore, prevent corrosion on electrical connectors. Being non-conductive, it does not enhance the flow of electrical current. This property makes it an ideal lubricant and sealant for the rubber portions of electrical connectors.
Dielectric grease is typically a translucent, grey substance that is insoluble in substances such as ethanol, methanol, mineral oil, and water. It is soluble, however, in the industrial solvent methyl ethyl ketone (MEK) and mineral spirit. It is important to note that dielectric grease will melt silicone rubber over time, and thus should not be used on connectors, such as o-rings, that are made of this rubber.
While the indicated use of dielectric grease calls for it to be used only on the non-metal parts of a connection, it has been shown to be effective at preventing corrosion when applied directly to the metal connectors as well. Care should be taken when using it in this way, because this application can, in some instances, cause the connection to stop working. A common reason for such a failure is that the grease has not been pushed entirely out of the way between the two points of contact.