Recognizing Roof Galvanic Corrosion
 

As many of you know, some late model Hi-Lo trailers are afflicted with galvanic corrosion of the aluminum roof. This appears to be caused by steel nails or other fasteners that contact the underside of the roof. Over time, the combination of steel, aluminum, and natural moisture results in galvanic or dissimilar metal corrosion. This starts on the underside of the aluminum roof and eventually goes all the way through. My trailer (2009 model) has this problem.

There are some things that you can look for to determine if your roof is corroding before the corrosion creates a hole. First, start by thoroughly washing the roof. Scrub it with a medium stiffness brush. After it is clean, carefully examine the whole surface of the roof. On late model trailers, the roof is made from textured aluminum sheets that are painted glossy white. Look at the roof from different angles to see if there are areas that are dull and not glossy. Usually these areas are small, and range from 1/4" to 1" in diameter. If you spot any suspicious areas, run your finger over them and feel if they are a bit rougher than the surrounding roof surface. If your roof has dull, somewhat circular areas, corrosion has probably started. If the area also feels rougher than the surrounding area, the corrosion is pretty advanced.

My trailer's roof has 4 rows of corroded areas. They are located on the left and right side of the roof, 2 to 4 inches in from the edge of the roof. They run fore and aft for 12 to 18 inches each. In all but one area the corrosion had not yet penetrated the roof. The one penetration was originally about 1/8" diameter, surrounded by a rough area of about 1" diameter. I poked a bit at the hole and discovered that the underlying aluminum had been reduced to aluminum oxide powder for about 1/2" diameter.

I eventually may need to replace my roof because the corrosion won't stop with a surface repair. In the meantime, I decided to use EternaBond RoofSeal tape. I applied the tape per the instructions to all the affected areas. Before applying it to the hole I enlarged it and dug up all the loose aluminum oxide powder. I then filled the hole with quick setting epoxy. After this set, I applied the tape.

I recommend that those of you with late model trailers inspect the roof a few times per year. Catching signs of corrosion before it penetrates the roof will prevent water damage to the interior.

Thanks for that, Raul.

I will "Amen" Raul's post...been there and done that. If you discover the 'metal rot' [electrolysis] early enough you may prevent the need to do extensive repairs to your roof and ceiling . If you do see the signs Raul describes early enough and use the EternaBondRoofSealtape used in conjunction with an elastomeric paint like KoolWhite, you will save yourself a lot of headaches later.

jcurtis95