My Barth is in great shape except for a few spots where oxidation is creeping under the paint. I would like to touch-up these areas, but don't want a hokey looking patch job. Can anyone discuss the the best process for this job. I would like to do it my self, but need advice.

Bill G

Hi Bill, I am a body man from my early teens and let me tell you that what I have learned is touch ups usually show as exsactly that ....a touch up ! If your just patching a strip then redo the whole stripe in the best possible match to the end or break in the stripe. If it is a large body pannel it is tough to match "dead on colors" depending on color ! Body shops can do a blend of new color into the old but without any garranty of match. What is the color first ? Reds, greys, blues and yellows are bad faders. White turns creamy/yellow with sun years too. Couls this simply be compounded to look good again ?

Kelly

Hi Kelly,

Thanks for the good info on touch up. There are some pictures of my coach in the Genturi post in this Tech Talk section of the forum. The areas that I have a problem with are various. One area in particular on the front passenger side is right at the edge of the strip joining the upper and middle body panels at the front radius and around the side mirror attachment. I scraped and sanded the bubbling paint in that area to try to stem the continued oxidation. I was concerned that it would eat through the aluminum.

I would need to paint the whole coach as there are areas like this (all smaller) here and there all around the coach. That is not an option financially at this time. My feeling that a touch-up is better than leaving it continue to oxidize.

I have all the Sikkens paint numbers and was thinking I would use an airbrush to do the touch-up. Is there a good product to put on the bare aluminum to stop the oxidizing prior to painting.

I'll post some pictures of the problem area, the Photobucket website is down right now.

Bill G


[This message has been edited by goodwinw (edited July 22, 2005).]

Good idea Bill on the air brush gun to try and blend/paint the stripes. This really is your best bet on making her look its cleanest. First make sure your metal is sanded with light grade sand paper. maybe work your way down to a 320 or 400 grid paper after your blemishes are sanded away. Then you need to zinc chromite the metal using your airbrush gun. It will be a two part yellow/green product (at least here in Canadian Napa store it is) Apply thins coats between drying. You can now fill any scratches with glaze or best would be the two part scratch fill. After you sand down the scratch fill/glaze you then apply regular primer....sand again and paint the area. Paint with light coats fooging it off towards the better part of the paint or stripe. Bill, when you are sanding on the final sand you can use a green kitchen scrubby on outside edges of your work so you can fog the paint into that area and have it stick. Be sure to degrease the areas worked and passed with a mild cleaner. You don't want any fish eyes or dots in youy nice paint right ?

Hope this doesn't discourage you because if you fallow the steps your job should be very nice. Then repaint your rig at a later date ...or not !
I will always say that the best thing you can do is take the time it takes to sand out scratches and use glaze. You will be proud you took the time when the job is done. It i stime consuming absolutley so good luck to you.

Hope I helped, Kelly

Kelly,

Oh goodie, another project. Thanks for your advice, it sounds right on.

Bill G

If you have corrosion under the paint, it really needs to be treated or absolutely completely removed before the primer goes on. My friends at the Confederate Air Force use mechanical means to remove the corrosion and smooth the metal. Usually a rolok disk from 3M. My own preference is to use combination of mechanical and chemical to remove as little metal as possible. I power sand a little, poke it with a fiberglass or stainless brush, and then use an acid wash such as Alumiprep or Metal Prep. Grit blasting works, too. The PPG version of Alumiprep is DX533 or c-2200 metal-sol. In the past, I have used phosphoric acid and even muriatic acid, but you gotta be careful with that stuff. Either way, passivating the metal with a chromic acid product like Irridite or Alodine before the primer is a good idea.

http://www.aircraftspruce.com/catalog/cspages/alumprepaint.php

As far as primers, the old standby is zinc chromate, but it is deadly if you breathe it. Same with strontium. It is also getting harder to buy. When Consolidated Aircraft Coatings combined with Randolph, they took the chromate out of their epoxy primer. Too bad, it was an excellent product.

DuPont two part Variprime (looks like zinc chromate, is self etching & contains zinc).

The Stits epoxy primer contains anti corrosion compounds and has a good reputation.

Bill G.
I know exactly what you are wanting to do, and having done my share of body and paint work, I can tell you it ain't going to be a picnic. The sanding and FEATHER EDGING of the paint is by itself nearly an art. Most of us know you well enough to know you want it right and rightfully so, your pictures of your table and now the exhaust extension paint a clear picture of your ability to peform. Is there a compartment door you can start with? Of course a door would be a solid color but when you get into some of the BLUES then you would possibly need to do what we used to call, CHEATING. That is when the color did not match perfectly and we would kind of fog out further in the body to make the difference less noticeable. Kind of fog the color difference. Personally I would talk to a PRO PAINTER and see if you can have the areas ready for color and let him do the actual painting. You also have to be concerned with dust, bugs, and LEAVES, remember them from your roof project.

You don't need me to tell you how poor paint work would look. You could always pratice on some pieces of metal and hold up to your coach to judge for yourself. I am NOT saying you shouldn't TRY.


I wish you well, and keep up informed.

Dale

I knew I could count on getting the advice I need on this project. I do have a friend in the business who can do the final paint and will work with him.

My issue is getting it ready; cleaned, sanded, neutralized and primed. This is where a lot of the work is, and I believe that I can do that part effectively.

Let's just deal with the first step. removing the corrosion and neutralizing or passivating the surface. What is the best way to apply the Alumiprep or what ever I end up using?

bill h, I like the idea of some sanding and some chemical to avoid removing too much metal. Could you you be more specific on the procedure on this part?

Bill G

Bill, I use a 2 inch Rolok disk in a die grinder. I can't remember the grit, but everyone is a little different, anyway. I use the disk until about 50% of the metal is shiny, with corrosion still down in between the shiny spots. Then I use a stainless steel toothbrush, followed by a fiberglass pencil brush, followed by the acid. Some folks use a Dremel mototool with a stainless wire wheel in it. Be sure not to use ferrous steel brushes. Whatever product you select will have its own instructions. I keep using the acid until the metal is all shiney. Then I apply the Alodine or Irridite, following its instructions. Use only distilled water with these products. If you use zinc chromate, or strontium whatever-ate, wear a really good mask and apply only a very thin coat. Some like a layer of epoxy primer over a thin layer of zinc chromate.

This is just my way, and even the experts at the CAF do not agree, because it is an individual thing. They spend hours a day working on old airplanes a few miles from the ocean. I think they grind away too much metal, but airliners and warbirds have thicker metal.

And Dale is right about it being hard to do it right. An airbrush can be very handy. Consider also a touch-up gun. It is between a regular gun and an airbrush.

And metallics are even worse.