Corrosion

[Zugbug]

I just noted what looks like a spot of corrosion under one of the upper running lights on my 2002 Bambi. Upon climbing up to get a closer look, it seems that I had a white powdery substance that I was able to clean off. The clearcoat does seem to be damaged in this spot. Spot is about 1/2 in by 3/4 inch. I have looked through the forums and seen fixes from aircraft anti corrosion material to clear nail polish. Any thoughts?

Zugbug
19' 2002 Bambi
2003 F-150

[GlenCoombe]

The first thing to check for is why! Is the spot adjacent to a hole? Dissimilar metals are the first spot for galvanic electrolosis. If AS or the PO used a steel screw to attach the light to the surface skin that would be a source for corrosion to start....

[Zugbug]

After speaking with a service rep at Airstream I am going to try using the clear finger nail polish trick. My next question is, I need to remove a running light as the corrosion seems to be starting from under it. How do I safetly clean off the Vulkem without damaging the clearcoat?

Zugbug

[Zugbug]

Does anyone out there know how to remove the running lights on a 2002 Bambi. I need to get under 2 of them to treat corrosion.

Zugbug

[mswartz]

Zugbug,

What you describe is called aluminum filiform corrosion. My 2001 19-ft Bambi has this as well. I first noticed it in 2001, a year after taking delivery of my Bambi, and I've seen it on many Airstreams of my model year and newer.

For your reference, an outstanding journal site on the technical aspects on filform corrosion is from the Journal of Corrosion Science and Engineering: http://www2.umist.ac.uk/corrosion/JC...r36/v2p36.html complete with pictures and a thorough discussion of the process.

The corrosion often, but not always, begins near a cut in the skin, for instance, at the edge of a panel or at a rivet hole. But I have also found this corrosion starting on a panel surface with no hole or edge.

Once it starts, there are two ways to deal with this corrosion that I know. Either I have to strip away the plastic coat surface from the entire affected area and a small perimeter around it, and then keep this polished, or I apply a chemical developed to deal with this.

It is important to note that filiform corrosion does not originate from the action of dissimilar metals, and is not going to cause a structural failure or problem. It does cause a cosmetic problem, as you are well aware.

The corrosion begins from the action of water and chlorides found in the air gaining entry between the plastic coat and the aluminum, and can proceed quite rapidly. It can start in conditions where a surface has never been wetted, only exposed to humidity.

To stop the corrosion when it has begun, for the past 14 months I've been using a chemical called Corrosion Block, also known as ACF-50, made by Lear Chemical Company, Mississauga, Ont. See their site at: http://www.learchem.com/five.htm. This was developed for the aircraft industry, and it has been available for other uses as well.

The aviation product is ACF-50, for Marine and industrial use the tradename is "Corrosion Block" and for automotive use the tradename is "Rustblock." The technical specification is in a PDF: http://www.learchem.com/images/Tech%20Spec.pdf .

Yesterday I did a close inspection of my Bambi, and found several areas where filiform corrosion was starting again along a previous track. I reapplied the ACF-50 again to all known sites yesterday after that. I am pleased with how this product is working. But I have to keep up on it.

I've taken literally hundreds of closeup digital pictures documenting this problem on my trailer to understand how the corrosion has progressed. I've attached an example from my Bambi.

Contact me if I can assist further.

[markdoane]

Marshall,

A fine description fo filiform corrosion, and certainly from your picture you have a classic example.

However, from the description Zugbug provided, it sounds more like exfoliation (intergranular) corrosion. The thing that bothers me is the description of a white, powdery corrosion product which could be cleaned off.

Regardless, I think the product you recommended, ACF-50, should work on both types of corrosion.

Maybe Zugbug could post a picture for a more definitive diagnosis?

[mswartz]

Mark,

You are right; her description does not mention the corrosion being under the coating, but in a couple of instances on my trailer the clearcoat has come off and the aluminum chloride is white and chalky at the surface of the corrosion area.

The first location I found filiform corrosion on my Bambi was around the tail-lights in 2001, and it appeared as she described. I took the trailer to JC in June 2001 and all four quarterpanels were replaced under warranty; at the time it was the first they had seen this I was told. It was clear that the taillight bezel had caused a break in the clearcoating to expose a spot starting corrosion.

If Zugbug looks closely around every rivet, edge and penetration, she may find more filiform sites. Most of mine look like the following picture (click on the picture to see enlarged view):

[Zugbug]

Great information, and yes I have this problem under the tail light bezel also. By the way this is a He LOL. Your photos look exactally like the corrosion I am seeing on my Bambi. I will try some of the product you mentioned.

Zugbug