Can rust be detected without going to the bare metal?

IMO the condition of the car will decide weather it needs to be a bare metal respray, IME bare metal is only required when the paint has some problem like crazy cracking or sever scratches/chipping. If the paint is in excellent order and this is just a freshen up then no need to go back to bare, but by the sounds of the doors I would definitely go back to bare just to see what’s under the paint in that area, the rest of the car will be up to you.

An experienced paint shop will be able to tell by walking around the car for 10min if it will need to be all over bare metal or just in some areas.

 

Hello,

problem with respray with modern paint materials on older Ferraris up to approx. 1980 is, that back then they used TPA ( ThermoPlastic Acrylics ).
Just respraying onto this kind of paint will definitely result in cracks. Nowadays there are special isolating primers which allow modern acrylics on TPA. But the painter has to know what he is doing.
Problem in the past was, that barely someone even was aware, that TPA even exists.
With 308 Ferraris one can - carefully - state, that the carb cars and 2V-injected cars manufactured in 1980 are painted TPA, and the later cars with modern acrylics. If there's a Glidden Salchi paint sticker, it's TPA. If there's a Glasurit paint sticker, then it's worry-free modern material.
Another method to determine TPA vs. modern acrylics is to rub a hidden spot with a rag soaked with laquer thinner. If the paint comes off, it's TPA. I tried this on my car inside the doors.
BTW; same problem with classic US cars, Jaguars, Rolls Royce and even mundane Opels. The latter which came from the Antwerpen GM factory were painted with TPA, the same models coming from the german Bochum factory were painted with with 'normal' paint.

Best Regards from Germany

Martin

 

Most of the time rust starts on the inside of the metal from moisture trapped in the bottom of a door or rocker panel. The paint starts to bubble once the pinholes of rust start to appear meaning the panel has rusted through from the inside. The rust on the inside needs to be treated/removed otherwise it will come right back.

 

And sadly,

There is almost NEVER such a thing as "Rust in just one spot.................."

 

Gotta agree with Martin here...

If this is an older F-car, you need to bite the bullet ($$$) and start over with bare metal. Re-painting over the older cars' paint (regardless of how good it may look) is ultimately money down the drain. The original paint will eventually go south underneath --- it's just a matter of when. As with all painting, the thing that matters most is preparation and condition of the substrate which you are painting. The old TPA paints provide a poor foundation for a new overcoat of any type of paint.

Depending on the degree of rust areas you already have to strip / prep, you may find that it won't cost too much more just to strip the entire car.

Stripping is also a candidate for a do-it-yourselfer looking to save money (and with alot of free time on his hands). I stripped an old Triumph of mine years ago, and let's just say that when I had finished I felt as though I had an "intimate bond" with that car.

Oh yeah, it's not something I would ever want to do again!

 

Ditto, and the only way to repair body cancer is by cutting out all of the rust and replacing the metal.

 

What are they hoping to get for the car? ($$)

 

I would only go to "bare metal" as required....IMO..

Martin has it correct, a knowledgable painter will apply the proper sub sealants and go forward.. in any case I would leave factory fillers in place....lead work also.

Get into that lead, exposed, and you have big problmes here in the USA......
so I'd say somewhere short of bare metal UNLESS an insurance company will bear the huge labor expenses involved....

I'm getting ready to go with some major paintwork, I'll update with my new painter's opinions, my older guy (now retired) was always adamately against any "strip to bare metal" jobs, and he was excellent with corrosion repairs....