PS Advisor June 2008 Issue

Tinned Wire Myth Busted

Well-sealed connections key to wiring durability.

I recently purchased an older boat. Not long before the purchase, the previous owner had the wiring replaced.

Tinned Wire
Using a conventional crimp terminal leaves the conductor ends exposed (above). Below is a conventional terminal that has been covered with sealing heat-shrink tubing for a water-tight connection between the terminal and the wire stranding.

All the workmanship seems to be in good order, with all connections and terminations made with Ancor crimped connectors and sealed in shrink tubing. All the wiring is the proper gauge (AWG) stranded wire.

The only problem is that the wire used was not marine-gauge tinned wire. I am wondering what the risks are to leaving it as it is. Clearly to rip it all out and do it again would be very expensive.

I am not using the boat that much and don’t intend a circumnavigation any time soon. If the connections are well made and the wire sheathing remains intact, what is my risk of wire corrosion with the un-tinned wire in a marine environment?

 

Steven Krenz,
Vilya, Catalina 25,
Corpus Christi, Texas

 

The matter of tinned wire being the only type accepted as "marine grade" is rather interesting. Ancor was perhaps the first vendor to the boating market to supply tinned copper wire and label it as "marine grade." It was a brilliant marketing move because now many people think that tinned wire is the only legitimate wire to use on boats.

In fact, many boaters are of the belief that the American Boat and Yacht Council mandates the use of tinned wire in its electrical standards. Well, this whole matter falls into the maritime legend category.

 

First, the ABYC does not mandate the use of tinned wire its standards—never has. Second, the vast majority of production boat builders still use un-tinned wire in their electrical systems.

Is tinned wire better? Well, it is more corrosion resistant, but the truth is, the un-tinned wire has been used for years and provides a more-than-adequate service life in most cases. 

Tinned Wire

The trick to enhancing the corrosion resistance with un-tinned wire is simple: Be sure that the terminations on any cabling in your boat are hermetically sealed. Standard crimp connectors don’t do the job. They leave the wire ends exposed to moisture, and eventually corrosion will begin at the terminal and migrate into the conductor as the moisture tracks up the wire under the insulation via capillary action. By using heat-shrink crimp terminals or adhesive-lined heat-shrink tubing on conventional crimp connectors, you can effectively seal the ends of all the wire on your boat.

Without exposure to moisture or salt air, the un-tinned wire will last as long as the tinned. (A good online source for heat shrink products is www.nationalstandardparts.com.)

To determine if your wiring has been affected by moisture, cut off the terminal on a suspicious wire and strip back about a half-inch of insulation. If the wire is black, and not shiny pink, then corrosion has begun to migrate along the conductor. You’ll need to strip back the wiring until you find clean, pink copper. Usually this requires stripping back no more than an inch or so of insulation. Snip off the corroded wire and install a new terminal as described above.

 

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