Process for tackling rust spots (mainly bottom) without having to respray?

Not looking for Concours respray. The car looks great from 10 feet- but rust spots on bottom doors are very noticeable. What is the process for tackling "eaten-through" rust spots without having to respray entire car or doors?

 

You could possibly use some 'tiger hair' or fiberglass repair to the areas, or fill them with bondo...

Not the proper way to take care of it by any means, but it may look maybe ok.

 

There is only one way and that is the correct way. Grind back/cut the old rust out, weld new metal in as required, fair and and respray. Any decent body shop will be able to colour match, providing the rest isn't too far gone so only respray the doors. (Don't worry about "concourse" there is a world of difference between a good body shop and one that can do "concourse".)

You "can" do it as mentioned above, but it will come back worse, and if you do ever sell it any basic inspection will pick this up and you'll then have to take a big hit on asking price as people will think a) I've got to fix that, and b) if he bodged that repair what else has been bodged....!

My advice is do it right first time.

 

2nd - and no matter what, some paint will be involved. However, a decent shop can blend the bottoms of the doors without having to spray the whole panel or car.

 

Great! I've been to too many shops that say a total repaint is required. I know it's a Ferrari, but everyone thinks it's gotta be a $10K paint job or it's not worth it. So, what is the operative word I should mention..."blend"?

 

Any decent paint shop should know what to do; if you have to tell them...walk away.

I’d look for somewhere that does classic cars, I’ve found them more “sympathetic”.

 

TBH, that's not the correct way, but it may be OK for you.
A full respray is not required to repaint a door bottom "correctly," but a blend into adjacent panels is. Body shops may not want to take on a job where the end result is more subjective. Tell the shop what you want done and find one that can explain the difference.

 

Depends upon the level of finish the OP wants. Anything can be done - just individual spots, the whole bottom edge and blended above, everything below the bodyline on one end of the door and blended into both the rest of the door and the next panel.....
Ability level of the painter is also a huge factor. I've seen both ends of the spectrum.

 

New to the game so I have no expectations for what it (a repair and paint blend) should look like. Is 100% match possible for a 'blend" job? Just don't want to pay for a full-blown respray of the whole car if I don't have to.

 

The reason to blend color is that there is no 100% match. The more / larger the blend the less chance the mismatch will be noticeable. Some areas like below a belt line are much harder to see, so experience and owner expectation are important before deciding what to do.
The other issue is clear coat and where the clear coat stops. Painting an entire panel is the best practice. Spot repairs of clear are much more likely to fail and / or be noticeable over time. That said, a 308, for example (which commonly has rust on the door bottom,) would be a good candidate for a spot repair for the stated reasons.

 

You can bodge this and get a good outcome as a do it yourself project.

What you do is sand down the rust by hand, minimizing the surface scratching around the rust spot. Use a dremel tool to grind rust away more fully the area if that helps. Then, use some Naval Jelly (by Loctite), which will remove any residual rust. Then, get some epoxy putty, JB Weld makes good product, to fill in pits or outright rust through, try to get as smooth as possible and minimize the further sanding, it gets hard. It cures quickly, then sand down as smooth as you can. Feather the edges into the surrounding area using some 800 grit wet sandpaper (maybe 400, followed by 800). Sand further with 1000 wet a bit more around the overall repaired area, and you are ready to spray.

Then you get a spray bomb from this place assuming you have your paint code. https://www.robertspaintcare.com/ You spray the area and a little around the area, first with the etching primer, then with the base coat.

Here is the secret key to the outcome...before the spray dries, you spray the blending solvent (Roberts supplies this as well), this "melts" the paint before it hardens and blends it and the inevitable overspray into the surrounding paint. You then do the clear coat, and the same blending solvent before it dries. Even a slight colour mismatch, from oxidation of the older paint, can be blended in reasonably. Hard to get a perfect match against old paint, but door bottoms take less of the oxidation brunt that the top of the hood lid for example.

Once this is all done, you wait a couple of days for things to cure, then get an orbital buffer and some light polishing compound to complete the blending, wax, and you will have a pretty nice repair, perhaps shockingly nice. Then, spray some Krown type rustproofing spray on the behind area of the repair, assuming you can get access through the inside door panel. This will limit any rust reforming from moisture creeping behind the repair, if you are sealed from behind and painted on front, and removed all the rust, it should last without further rust bleed through for a very long time.

I have done this on a couple of cars over the years, it does require some patience and meticulousness, but I can tell you, done well you will not detect the repair, it can turn out that well.