Boat trailer corrosion

Several years ago the pressure treated lumber industry changed from infusing boards with chemicals with an arsenic base to salts with a copper base. Both types do a good job of keeping teated lumber from rotting when exposed to the outside elements.

After the change-over, carpenters learned they couldn’t continue using galvanized or plain steel nails or screws with this lumber. When copper salts in the wood contact bare steel, electrolysis starts quickly corroding (rusting) the exposed metal. In most environments, a 16 penny nail or standard decking screw will rust away in less than a year.

Evidently some boat trailer manufacturers didn’t get the word, or didn’t care. At least the trailer company (Michigan based) that built mine didn’t.

My trailer is over 10 years old and has well over 100,000 miles on it. There are enough dings, scratches and road-hazard marks on it that it doesn’t look show-room fresh. And maybe I didn’t spend as much time crawling around under the trailer inspecting the bunk supports as I could have. But who does?

So when I noticed a couple of the lag bolts that secure the bunks to the supports coming loose I crawled under to tighten them. Tighten what?

There was nothing left to tighten. The 5⁄16-inch lags were rusted to oblivion. To make matter’s worse, the corrosion infected many of the brackets through which the lags screw to secure the bunks to the frame. What started as five minute fix to tighten a few lag screws is now a major and expensive reconstruction.

If you have a bunk-type trailer, take the time to physically crawl under it for an inspection. If the lag bolts show rust, swap them out with lags made of stainless steel. If, as on my trailer, the corrosion is more extensive, make the repairs and be sure there’s a gap between the steel and wood when re-installing. I’m using thick, nylon washers.

Categories: Blog Content, Michigan – Mike Schoonveld

Leave a Reply

Your email address will not be published. Required fields are marked *