"BUBBLING" on my panels

[jmayaa]

Within the past year or so several areas on my CT have started to "bubble up" under the finish. I'm sure it's some type of oxidation or something like that.
What, if anything can be done to stop what has already started and what can I do to prevent any future areas?
The crazy thing is, I'm only seeing this on the side door.
As the pics show, some is just around the screws while some is starting around the one hinge.
In the past, when the factory fasteners started to rust, I replace them with stainless fasteners the same size and style.
Any suggestions sure would be welcome, it's really starting to look crappy....
Thanks in advance...
Jeff

[QueticoBill]

Whats the red skin-aluminum? Galvanic action maybe?

[McDave]

Hmmmm.... definitely corrosion. Electrolysis is the first thing that comes to mind. The fact that it bubbles beneath the paint is a clue. The paint was not previously damaged in those areas, and yet corrosion set in. The activity is taking place somewhere behind the paint. So first, is there a drip rail over the door? And does it divert the water away from the door? I suspect that there is water infiltration into the door, and the insulation (probably styro foam) is holding that water. The reason electrolysis comes to mind is that the door is isolated electrically speaking from the rest of the trailer by rubber seals and air gaps and gaskets, therefore it may have a slightly different charge than the rest of trailer that is tied together at ground. But the proximity is so close that a state of flux begins wherein everybody wants to be equal so a charge is being passed from one to the other. The water is the conductor and until it has all been used or removed the activity can continue. I would have to do some exploratory surgery on the door just to see what is going on in there. The white powdery residue coming out of the bubbles is very similar to the corrosion that is found on battery terminals...The only other time I have seen aluminium react in that way was to caustic soda. But how could that get in there?
But then again, I could be wrong. Perhaps ol' Hank has seen this before...

McDave

[hankaye]

jmayaa, Howdy;

Within the past year or so several areas on my CT have started to "bubble up" under the finish. I'm sure it's some type of oxidation or something like that.
What, if anything can be done to stop what has already started and what can I do to prevent any future areas?
The crazy thing is, I'm only seeing this on the side door.
As the pics show, some is just around the screws while some is starting around the one hinge.
In the past, when the factory fasteners started to rust, I replace them with stainless fasteners the same size and style.
Any suggestions sure would be welcome, it's really starting to look crappy....
Thanks in advance...
Jeff

Jeff, what you have is basic surface corrosion. The white powdery stuff is the aluminum 'rust'.
Best to remove the paint from around the area to see what the extent of it is in each area,
maybe an inch out from what you can see at each spot. You can either use a stripper (masking off each spot),
or use some automotive type abrasive paper, 120 grit to get the paint off then 220 grit to feather the edges.
See if you can find some Alodine https://www.google.com/search?q=Alodine ... 8&oe=utf-8
to treat the surface with, then prime, and paint. The reason for the Alodine is to re 'clad' the aluminum,
the coating that most likely was broken during the manufacturing process (it happens), One tip about applying
the Alodine, it needs to be applied to what is known as a water-break free surface. The translates to a surface
where the water 'sheets off' and doesn't leave dry spots with borders. We used to use a light amount of
Comet or some other scouring powder, just be sure you get ALL of it rinsed off.
Hope this helps.

hank

[jmayaa]

OK guys,
Any thoughts on how to refinish these areas and try to get them even close to looking like the rest of the trailer?
If not,
I guess something close would be better than having the aluminum skin get totally ate away....
Thanks everyone for your help and suggestions...
Jeff

[hankaye]

jmayaa, Howdy;

To finish off the process it's a simple matter of prime and paint after you've rendered the corrosion
and re-anointed the aluminum with the Alodine that I mentioned in my previous post. If there are
voids where the corrosion has eaten away more then a layer of metal then you could use some Bondo
to smooth out the surface prior to priming and painting.

ahnk