I have an older Barth that was resprayed probably 10 years after it's inital painting.

The second paint job has chalked a bit, and it coming off in places exposing both the original paint underneath, as well as bare aluminum in places. I have done some research on painting Airstreams (there was a great thread on the Airstream forum) but have discounted that advice because using the materials suggested would be well out of my league (probably 3k in materials)

I am looking to do this for under a grand. I have done a lot of reading and talked to some paint people and settled on a possible solution.

PPG makes an industrial paint formulated for both galvanized steel and alumminum. It is sold by the gallon and has an activator that is mixed into it.

I am not looking for ultimate gloss, but a nice durable finish that won't be a total embarrassment like the current faded, flaking mess.

Will keep you all posted..

The key is ALWAYS preparation and the use of a suitable primer. In no way would you be happy with the results if either is downplayed.

Preparation, preparation, preparation. Then when you are "finished", start again, preparation & preparation. You will not find a paint that will cover over a poorly prepared coach.

I know this isn't applicable here, but Ed Gilmore when to Mexico for his 40 footer and got great results for an excellent price..

http://barthmobile.com/eve/forums/a/tpc/f/363108706...711009061#5711009061

I'm gonna echo GG here on prep. Whoever sprays it, be sure they or somebody really sands it and addresses all corrosion or bubbling issues first. My Barth has a nice respray, but they didn't do a good enough prep, so I gotta go after the bubbles where corrosion continued to grow. Oh, how I wish Barth had done the passivate and zinc chromate thing.

This corrosion on aluminum is called "filial corrosion" - it was (I'm not making this up) originally thought to be caused by worms. It actually is minor corrosion, made to look worse by the lifting of the paint. Rarely is there any real damage. Proper surface prep of the aluminum (mainly thorough washing and drying) prevents it, and zinc chromate doesn't, although it may slow it down.

The best way to treat the corrosion is with a product called Alumaprep, it is an acid that etches the aluminum, then you treat it with a product called Alodine. This can be done in localized areas or entire panels. Epoxy Polymide primer is the best for adhesion and corrosion protection, though it is expensive and will probably blow your 1K budget buildup, however you won't need to prime the whole coach, just the treated, bare areas. This is how it's done in the helicopter business anyway. For the rest of the well adhered paint, thoroughly scrub with scotchbrite-very fine (burgandy) and wipe down well with lacquer thinner, and that will suffice. If you're looking for a bulletproof paint that's easy to work with, try Pacific Endura, its used on many of the seine boats on the west coast here, its a great product.

quote:

Originally posted by Rusty:
This corrosion on aluminum is called "filial corrosion" - it was (I'm not making this up) originally thought to be caused by worms.

I just spoke with Thomas Edison again, and he said it's called filiform. Filial corrosion is when your brother rusts when left outside.

But seriously, here is a link that alludes somewhat to the effectiveness of zinc chromate against filiform corrosion:
http://www.material.ntnu.no/elektrokjemi/korrosjon/adhesion/

They (of course) say anodizing is great, too, but that is not an option for us.

I have had good results with a combination of alodine and epoxy zinc chromate. Unfortunately, both epoxy and zinc chromate is quite toxic, so it is getting harder and harder to get.
We have seen an increase in filiform corrosion on our planes since zinc chromate stopped being used.

Some sources blame chlorides left on the metal or even the alloy itself. Still others will tell you you gotta bake the metal before treating, priming or painting. Magnesium control surfaces on Bonanzas need it for 24 hours.

I have noticed that Japanese aluminum on motorcycles is quite susceptible. Years ago, a Yamaha engineer told me that clears were the worst, because they couldn't use a chromate or strontium something-or-other under the clear. They had better corrosion resistance that way, but the customers wanted shiny aluminum, not painted.

A company in Germany claims to have a primer they cal PAni that is the first successful prevention for filiform. It a sort of polyanaline.

I also had good results with zinc chromate epoxy on Mercruiser outdrives (in salt water). (With a name like "Rusty", one has a natural affinity with corrosion).

My F35 Bonanza also had the zinc chromate option, but there was still some filial corrosion...

Yep on the prep. Many more knowledgable friends in the biz have said that a good paint job is 90% prep and 10% spraying.

There are some areas of friable paint, and I will sand them down and blend them in with surrounding areas. I plan on scuffing the top layer of paint til it is just about gone, and see how far into the bottom layer I need to go. I will use a good primer and have looked at several options. Probably will use the $$$ stuff on the few areas of bare metal.

Interestingly, the bodywork on the Barth seems to be pretty corrosion resistance. The problem I have found is with the doors of the compartments. There are a few through and through holes in my battery door cover. I plan on stainless steel rotary brushing them down to new metal, and use epoxy as filler. Sand and paint. I will experienment on the compartments first.

Have a bunch of projects planned, want it done by June..going to vacation then..

A great paint for aluminum is Interlux Perfection [EMAIL]http://www.yachtpaint.com/usa/[/EMAIL] I build aluminum boats and find that their paint stands up equal or better than Endura and is a bit cheaper and easier to apply. You must use their Viny-Lux Primewash 353/354 Primer. It is a 2 part zinc chormate Self Etching Metal Primer that is great for use under most 2 part paints. The key to any paint job is the primer. On aluminum, the most common failure is between the metal and the primer. The best prep method is to sand blast the aluminum and then air blow or better yet pressure wash with plain water. Never touch the prepped aluminum with anything. A cloth or even a tack cloth will leave tiny threads or hairs that protrude through the paint and act like a wick that will allow moisture to penetrate under the coating.

quote:

Originally posted by FUNKYWAY:
A great paint for aluminum is Interlux Perfection [EMAIL]http://www.yachtpaint.com/usa/[/EMAIL] I build aluminum boats and find that their paint stands up equal or better than Endura and is a bit cheaper and easier to apply. You must use their Viny-Lux Primewash 353/354 Primer. It is a 2 part zinc chormate Self Etching Metal Primer that is great for use under most 2 part paints. The key to any paint job is the primer. On aluminum, the most common failure is between the metal and the primer. The best prep method is to sand blast the aluminum and then air blow or better yet pressure wash with plain water. Never touch the prepped aluminum with anything. A cloth or even a tack cloth will leave tiny threads or hairs that protrude through the paint and act like a wick that will allow moisture to penetrate under the coating.

I would guess the type of sand in the sandblasting would be critical...

I believe that sand is too hard for soft aluminum.

Glass beads, walnut shells and plastic media are best.

Coupled with the fact that sand creates dust attributed to a lung condition called "silicosis", symptoms similar to black lung or asbestosis.

Breathing appartus is required, no doubt!

I use good old silica sand on a regular basis with no problems. The only thing to consider is the alunimum I use is 1/8" and thicker. On the thin skin of a coach one could peen and warp the sheet. In this case a softer media such as walnut or plastic bead might be better. And yes you do need a air supply hood for all blasting.