What's eating your trailer: where differing metals meet, things can go wrong.
One thing many boaters don't pay enough attention to is the effects of galvanic corrosion on trailers. Sure, most of us know the benefits of a thorough washdown with soap and fresh water. Even with diligent care, however, there are places where corrosion creeps into the system.
One common problem arises at points of direct contact between dissimilar metals, such as aluminum and steel. In the presence of salt water, electrochemical reactions between the two metals result in corrosion of the metal which is less-noble (more anodic), ranked by its position on a galvanic series. In the case of aluminum and steel, varying grades and coatings--and varying surface areas--can mean varying results. Sometimes the steel wins; sometimes the aluminum. Over a long period, destruction may be, well, mutually assured.
Premium stainless steel bolts and other fasteners purchased from a reputable trailer shop are well-protected from galvanic corrosion because of their chromium content. But for beams, brackets and other large, load-bearing components, stainless steel is impractical for most trailers--too expensive, and difficult to find.
Aluminum-frame trailers are very common in Florida, as aluminum stands up to salt water better than galvanized steel. Yet many aluminum trailers are built with galvanized steel bunk brackets and other components. Galvanized steel, of course, is steel that's been treated with zinc plating or dip. The zinc acts as a protective anode, but it's not forever.
The photo at left shows a gory example of what may happen when the zinc on galvanized steel breaks down: The galvanized "hat bracket" in the foreground has suffered fatal corrosion. It split. Had this occurred while trailering on the highway, the aluminum tube (itself oxidized and deformed) supporting the bunk above it may have dropped several inches--the boat may have crushed a fender into a tire, leading to a blow-out, leading to ... you get the picture.
Fortunately, the boat-owner recognized the crack during routine inspection of his trailer. He'd noticed some rust spots here and there, and decided to put his boat in a temporary dockage to do a full inspection and update of components, a good idea. Among other work, the boater replaced all 8 of his steel brackets with aluminum ones, at about $20 apiece. The job was an easy one, requiring nothing more than a socket wrench and a few hours.
Trailer companies with a long history in Florida are keen on minimizing these effects from day one.
Jeff Owens, of Aluminum Slide On/Ow-ens & Sons Marine in St. Petersburg, for instance, mounts bunks on top of the aluminum I-beams. This side-steps the points of metal contact shown in the photo.
Where aluminum and steel contact is unavoidable, as in the surface where a galvanized torsion axle is bolted to an aluminum frame-member, Owens recommends adding some form of insulation between the surfaces. A piece of roofing tar paper is one inexpensive solution, slipped in there before tightening bolts.
Another sleeper tip for minimizing corrosion comes from Tony D'Ippolito, Regional Sales Manager for Magic Tilt Trailers: Install ground wires for the trailer lighting system that connect directly to the tow vehicle. On most trailers, lights are grounded through the aluminum or steel frame; D'Ippolito says this current may accelerate structural corrosion.
When ifs time for annual service of your engine, take time to thoroughly inspect your trailer, as well. Superficial rust here and there is probably unavoidable for most of us, but if sheets of metal are flaking off, or aluminum beams are showing signs of deep pitting, you may need to replace these components.
Some other things to watch for:
Tires: Under ideal circumstances (kept at proper inflation, protected from sun and water, rolled periodically), the life span of a trailer tire in the Florida climate is about 4 or 5 years. There's a date of manufacture code on the sidewall. Heed it. (Look up the codes on the website for your tire manufacturer).
Wiring: Many new boaters become obsessed with rigging corrosion-proof trailer lights. Good luck with that. LEDs hold up longer than incandescent bulbs, but just go ahead and figure on replacing your wiring harness every year or two. It's inexpensive.
Bearings: Replacing the grease and seals once a year is good insurance. While you're at it, inspect the bearings and races for any signs of pitting or scoring. Replace if needed. Any squeaking or grinding from your hubs merits immediate attention.
Coupler: Make sure your coupler latches securely. As with many trailer components, replacing a coupler is inexpensive.
By Jeff Weakley, Editor
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|Date:||Mar 1, 2014|
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