Preventing Corrosion in Electrical Connections

Electrical and electronic topics for small boats
jimh
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Preventing Corrosion in Electrical Connections

Postby jimh » Mon Dec 14, 2020 5:08 pm

Preventing Corrosion in Electrical Connections

I offer some advice on preventing corrosion in electrical connections based on my own experience in working with electrical connectors and contacts for over 50-years.

I do not recommend using a wire-brush to clean electrical contacts. Most electrical contacts are accomplished with copper connectors or with copper connectors plated with tin or possibly silver. A "wire-brush" is usually made of stiff steel wires, and using such harsh abrasion onto soft copper or copper with a thin plating of tin or silver will cause scratches. To clean electrical connections use an clean toothbrush and a mild solvent like WD-40. WD-40 is not harmful to copper, tin, or silver, and will help to remove corrosion and other deposits.

To understand the basis for my advice, the goal is to reduce surface variations at the point of contact between the conductors. Any pockets or openings at the point of contact create a reduction in surface area. They also create opportunities for water to intrude into the connection and cause corrosion. Copper itself tends to be easily altered into a non-conductor by corrosion and oxidation, so the last thing you want to accomplish is to remove the tin or silver that plates the copper or to made the surface of the copper irregular. I also use very fine grit emery cloth, 600 or higher, and wet sand with WD-40 as a lubricant, to restore the surface of large ring terminal connectors.

Ring terminal connectors that are badly corroded should be discarded. Cut them off and attach a new ring terminal connector. Inspect the wire carefully, as the copper in the wire itself may have been also corroded. Sometimes, if enough slack wire is available, you can cut off an inch of the original wire to get to copper wire that is clean and dry. If not, use WD-40 and wet sand the copper wire itself with 600-grit emery cloth.

I do not recommend using a non-conductive grease such as a "dielectric" grease on electrical contacts. Electrical contacts or connections should be made with the two connectors dry and clean. If there is to be a sealing of the contact connection inside a connector, a non-conductive grease can be used on the connector seals. Since most electrical connections in an outboard engine are only carrying 12-Volts, it is not necessary to use a specialized grease with ability to insulate thousands of Volts of electrical force, which is what a "dielectric" grease is intended to do. However, there is no harm in using dielectric grease on the seals of connectors. But do not apply it to the contacts surfaces. Use it only on the vinyl or rubber seals of connectors.

To understand the basis for my advice, dielectric grease is intended to be extremely non-conductive; it is a great insulator. It does not conduct electrical current. Putting dielectric grease directly onto the contact surfaces of electrical connectors does not enhance the conductivity of those contacts. There are, in fact, conductive greases that are often used to enhance the conductivity of electrical contacts, such as BURNDY PENETROX-A, which is used with aluminum conductors. But dielectric grease is specifically designed to be an extremely non-conductive grease that can withstand very high voltage.

If the electrical connection is to be made on an exposed terminal post, the terminal connectors (and I hope there are not more than two of them) should be placed on the post dry and the retaining fastener tightened. To protect the connection from water, an aerosol spray-on film can be applied. The product BOESHIELD T-9 is a useful aerosol spray for this purpose. To not apply an extremely heavy coating as the T-9 tends to remain slightly tacky for some time.

PRACTICAL SAILOR tested many products intended to prevent corrosion and protect electrical connections on boats. BOESHIELD T-9 was said to have "...the best combined score for corrosion inhibition...and electrical protection" among the many products tested.

Cf.: https://www.practical-sailor.com/system ... al-systems

In some cases a paint-on insulating and protecting product such as LIQUID ELECTRICAL TAPE can also be used to create a sealed coating for an electrical terminal post connection. Products like this can be somewhat tedious to remove if the connection later needs to be changed or worked on.

Coating an electrical terminal post contact with grease after the connection has been made dry is also an option, but I do not recommend it. Grease tends to attract and hold dirt. Grease tends to melt at higher temperatures, as may occur on an engine, and can run off the the terminal post.