Filiform corrosion

Returning home from the shore, means it’s time to hose off the salt deposits from the trailer. It’s also the time for the trailer’s annual, big wash and wax job. This time, though, we knew it would entail more, and we’ve been preparing.

Ever since Randy (a fellow 23’2007 Safari SE trailer owner) asked the question, “Does anyone know what this is?”, on the Airstream Knowledge Sharing Forums, over a year ago, we’ve been watching for its appearance. We’ve been following the Airforums’ eye-opening thread, “Corrosion problems with new Airstreams“, for a year now. We’ve been quietly holding our own vigil, carefully inspecting our trailer for the inevitable worm-like filiform to grow from the unprotected edges, rivet holes and scratches in the aluminum skin and burrow under the clear coat where humid conditions help it to thrive.

Our filiform were slow to emerge, probably due to using a good wax last year, Meguiar’s Mirror Glaze, Professional Polymer Sealant, #20, as part of our wash and wax regimen. But emerge they did, white worm-like, thread-like filaments sprouting here and there along the belt-line area.


And from various rivet holes…


And on taillight housing bezels…


And wheel rims…


Using Google search, I found interesting background information on filiform corrosion and watched how it grows. I am learning that corrosion is a threat to all trailers and filiform corrosion is a threat to all aluminum trailers with a clear coat finish. As of this writing, there are 29 fascinating pages regarding this filiform issue on the Airforum’s thread, “Corrosion problems with new Airstreams“, along with strategies to control this condition.

This information helped us to select our interventions for the counterattack which coincided with our wash and wax job on our return from the beach. First, I washed the trailer with a good car wash and chose, Meguiar’s Deep Crystal Car Wash.


We chose and applied CorrosionX Aviation to the entire belt-line area, taillight bezels and wheel rims. I also applied CorrosionX to the stabilizing jacks, which were showing some corrosion. The following day, I wiped off the oily excess and sprayed on Boeshield T-9 (“Rust & Corrosion Protection, Waterproof Lubrication”, as stated on the label). I liked how T-9 dried, leaving a waxy residue. Meguiar’s Professional Sealant #20 was then applied and buffed.


Read Randy’s experience with filiform corrosion and his remedy: he took his trailer to Jackson Center where the Airstream factory applied the Classic Beltline Trim.

We’re hopeful that our interventions will be successful in protecting our Airstream trailer, while keeping it looking good.


  1. says

    Ohhh…that is one pretty trailer now. And certainly it’s better protected…who knew all that corrosion could happen? It makes me want to paint my house now even more than I did before…not that it’s corroded, but wood is a whole other problem isn’t it?!?!

  2. says

    Well Bill….I think I need to stop by with my trailer for the full cleaning. Here in AZ I can’t even wash it down! 🙁

    Trailer looks great! Keep posting!

  3. admin says

    In one of the references you linked to, I noticed that relative humidity below 60% is said to reduce the spread of filiform corrosion. Perhaps this explains why we have had so little trouble with it after three years of heavy travel, and many trips to the salty seashores. Most of our travel has been in dry climates where relative humidity above 60% is rare. Only for two or three months in the summer do we venture to the humid northeast. This seems a good argument for spending more time in the desert — where I like to be anyway!

  4. says

    just stumbled across your website. what great timing! we just returned from our first airstream road trip and i was just about to research how to clean it properly. thanks for the great information! look forward to following your blog.

  5. Guy Lariviere says

    Thanks for the great article. I’ve also applied basically the same treatment to my Airstream. I have a year old (2008) 17’ Safari Sport that had started to corrode. After the first application I can see where the Boesheild T-9 has already started to penetrate the corrosion. I live about 10 miles from the beach in S. California, so there isn’t allot of moisture in the air plus I camp out in the desert. The corrosion caught me off guard and I will be keeping a close eye on it from now on.

  6. says

    Bill, don’t know if my first attempt at emailing you went through. At any rate, just a note to let you know that your comments are much read and remembered in the Airstream community. A faithful reader forwarded this posting to me after I posted my images of filiform corrosion. So again, my thanks for your thoughts sent separately and for the information here.

  7. Bill D. says

    Bert, thanks so much for your comments to this post. Please note that while we are upgrading the WordPress software here, some of my images are not seen until the link to them is clicked.

    At any rate, I was pleased to be able to help you present larger images on AirForums, which illustrate your recent difficulties with filiform corrosion as you look for a solution. Best to you and Janie. — Bill