under door electrolysis

[pripaldi]

Greetings
Snow is almost gone so starting to get trailer ready.

Under door there is a small section that's rotting away.
This is the only section doing this.

Reminds me of my aluminum prop on the boat i used to have.

Anyone have any ideas on how to find the cause......thanks pete
oops just noticed the pictures are upside down.....duh

[OhioMark]

At a loss myself, but tt reminds me of road salt damage on aluminum.

[drcook]

See if that aluminum is bonded to something, or if water is sitting in behind it. We had a door on a Featherlite horsetrailer do that. One explanation given to us by the dealer was defective glue, my explanation was a design that let water fill up the door.

When I cut the skin off, it was full of water.

You could also see if it is touching something dissimilar, such as steel.

[Tim D]

Originally Posted by drcook

You could also see if it is touching something dissimilar, such as steel.

This would be my guess too. Water in an of it self will not do that to aluminum.

[harley]

you have to drill decent sized holes under all doors. they only put 1 or 2 small holes.

[pripaldi]

thanks for the suggestions, i played around , here is what i found.
Took out my meter, the strip under the door is grounded, as is my whole body and frame.

I removed the few screws on the small piece of trim under door and most were rusty. Behind the aluminum is a sheet of plywood that is damp/wet. Under the door threshold and under my trailer is covered with that black stuff. So i cant see whats under door, the cover is just about even with the end of the strip.

I also cant tell if that small strip thats rusting under the door is just a small separate piece or is part of the sheet metal on the other side of the door, cant see behind the side trim. (didn't want to dismantle the whole trailer on only one cup of coffee)

My first thought is water is getting behind the piece, either from door frame, or something leaking under floor. It near my fresh water tank.

BUT i just look at the other door and there is one small bubble growing there. I have hard time believing the same water is getting back there.

At some point ill have to remove the black cover under the frame and door or cut a hole it to take a look.

To keep the aluminum strip off the wet wood for now, I scrapped behind the strip up to and under the threshold about 4 inches up and put a piece of 1/16 plastic behind it. Don't want to cover it yet until i look into it more or have the dealer check it out with me.

That's where im at......need more coffee........pete

[Rhizoo]

Originally Posted by harley

you have to drill decent sized holes under all doors. they only put 1 or 2 small holes.

I don't have anything to add to this topic except thanks. As a newbie I had no idea that that under the door needed to be monitored and possibly to have holes enlarged. There is so much great help in this forum for us guys who are still at the bottom of the learning curve.

[Lloyd]

Originally Posted by harley

you have to drill decent sized holes under all doors. they only put 1 or 2 small holes.

harley, can you be more specific as to where you drilled the holes?
I can't say that I have ever heard of that before.

[Dayle1]

Behind the black plastic will be the floor structure which is plywood decking with aluminum floor joist that run front to back, insulation between the joists and the black plastic on the bottom and sides of the structure. The floor structure is attached to the steel frame using bolts thru the plywood and perimeter floor joist, these are carriage bolts that are under the wall. About every 4 ft or less you will see a steel 'outrigger' that extends from the main frame rail and at the outer end you will see the end of the bolt and the nut. Anyway, you probably don't need to cut the plastic to inspect behind it, that part of the floor structure will look no different than any other part, the location of the door does not modify the floor structure in any way.

You were not specific about the wet plywood, but I'm guessing it is just 1/8 inch thick lauan and installed with the edges top and bottom. My guess is that it and the aluminum skin under the door are just filler strips that are added to bring the surface under the door flush with the skin on either side of the door.

My suggestion is this, buy a roll of aluminum flashing, cut a replacement piece and paint it with a matching can of spray paint. Replace the 1/8 inch plywood with an 1/8 inch filler strip that will not absorb moisture, either 1/8 inch aluminum or plastic, maybe stainless, galvanized or rust proofed steel. Finally use new stainless steel screws.

The 1/8 inch lauan panel edge may be exposed along the entire length of the trailer, but elsewhere it is better protected from moisture by the curved skirting and the trim strip. Also, finding rusty screws is not alarming, every exterior screw has the probability of rusting.

[drcook]

removed the few screws on the small piece of trim under door and most were rusty.

Find a mom and pop fastener shop in your area, one that is willing to sell "by the piece" not "by the box". Lowes etc can be a bit pricey.

Then replace every exterior screw with stainless. Get some silicone sealant. Before you replace each screw, put a dab of sealant on it. You don't have to glob it up, but enough to seal where it screws in. After 1 or 2 you will have a handle on how much will be enough to even get a little under the head and completely seal the installation.

[harley]

Originally Posted by Lloyd

harley, can you be more specific as to where you drilled the holes?
I can't say that I have ever heard of that before.

I thought we were talking about the bottom of the actual door.,not the siding under the door. Anyways ,I noticed on another trailerthat after washing the trailer that when I opened the door ,water would run out of the factory drilled hole on the bottom of the door. I drilled a hole on the left and right side in the alum part of the door. That way water could run out if the trailer was tilted nose down or up.