For those that have only done limited body work or none for that matter. This is the kind of stuff you may uncover during your attempt at repairs. Here are a couple photos of the trunk lid for Sandy's Ravenna car. The trunk lid was replaced at some point with a factory white one. I assume during the process to replace the lid the shop did some body work to the used part. You will notice there is a patch of white paint left on the lid. That is where my first suggestion comes in. If I have to strip that much paint off a flat panel or any panel for that matter I strip the whole the panel. during the course of the repair should you get some filler up over the edge of the factory paint or any paint for that matter it will cause bridging. With the best of high builds you may even get a solvent line or shrink down after the paint is applied. You can wet sand and buff it out and it often reappears down the road.

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The second thing you will notice is where the factory paint is still on the panel there is no surface rust. I stripped the panel but I should have taken a photo first. The paint was full of popped bubbles. After stripping off the paint it was clear to see that the panel was left wet and moisture was trapped under the paint. this caused the top coat to eventually fail.

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So the only way to repair this is to strip off all the body work, finish stripping the factory paint and clean up the rust caused by an improper repair.

BTW: 90% of the filler was not needed.

Good to know!

Taking paint off an old car is like counting rings on a tree.

Or an excuse to wonder "WTF did the POs of this car DO to the poor thing" as you uncover years of fixes, re-sprays, fillers, rust etc.

Zach

"With the best of high builds you may even get a solvent line or shrink down after the paint is applied. You can wet sand and buff it out and it often reappears down the road."

Hello rick918-s, thanks for the great info. Please would you explain this in more detail, for a layman? Solvent line? Shrink down line?

Rick, I love this stuff. Thank you.

First: Zach.

Bugs: Ya, filler is softer than hardened paint. top coating filler that is blended into and over sanding scratches on painted surfaces with a solvent based product (primers, sealers, etc.) causes what is referred to around here as bridging. As the solvent penetrates to create a chemical bond it soaks through the filler causing it to swell or bridge or cause a false height in the products as it cannot soak into the painted surface at the same rate. After the products are blocked the same process occurs when the paint is applied. Later this is also blocked and buffed. Later when you bring the car into the sun on a hot day you will see the sun cause the solvents to lift again and show the scratches where you caused the bridging effect to start.

Hope that helps.

That clarifies it. Paint and finish work seems to be full of these little details that, if missed, can turn hundreds of hours' work into shitty results - all too easily.

More forensic auto body. Here is the underside of a rear lid I'm preparing for Sandy's Ravenna car. This is a continuing example of what not to do.

The first photo shows the improper preparation of the substrate before applying the color. Based on the color and chalkiness of the red oxide color I would say this is a generic lacquer based primer from the mid 80's. I used something that had the same appearance. The solids in the primer dried hard. Too hard to apply a top coat over without extensive prep work. You can see I simply removed the paint with a scrapper. There is no sanding scratches in the primer. Nothing for the top coat to lock onto.

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I stripped the primer off with a M.A. with 36 grit then 80 grit. I have stated in the past that if you have several sand through areas on your factory finish you should just strip it off to avoid the appearance of sanding rings. In this case I won't worry about this as the top coat is not exposed to direct sunlight. This will help maintain a stable finish.

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The second issue you will want to be sure and check is rust forming between the inner skin and reinforcement. Lots of these lids rust out at the latch because the factory placed a block of foam between the skin and the reinforcement. This lid is ok but I can see rust forming. I cleaned all the flaking stuff out that I could get to. Then I used ample amounts of converter until it ran out of every seam. I plan on getting a nozzle I can insert in the space between the skin and reinforcement and encapsulate any rust that may be present.

Almost need to acid dip these cars, then soak them in a rust converter bath so it soaks into every cavity.

In theory that sounds like a good idea, in practice, it isn't.

During the acid dip process, it's not possible to get the acid in contact with 100% of the material. You don't know what foams or fillers the factory has put inside the chassis. The cardboard and insulation heater tubes in the longs will be destroyed with no way to replace them.

After acid dip and neutralization, it's not possible to get all of the acid and neutralizer out. You'll also need to find the thin areas and repair before going any farther.

A rust converter or primer bath won't cover 100% of the material just like the acid dip. There will be air pockets that you'll never know about inside the chassis cavity.

True. But you can disassemble the car by removing the top of the long and removing the muffler/heater tube before dipping. Guys on the forum have done this. Getting the car dipped in a primer will benefit the process. True, you won't get the sandwiched metal between the spot welds but for the most part you will have a far better chance of a long lasting repair.

I have a car here that will go to a shop that will dip it, then give it an e-coat bath. I'm very interested to see how that turns out.

E-coat (electro-coating) is the way to go if available. We e-coat our coils for coastal and marine duty and it gets in all of the nooks and crannys. Coils are fairly easy in comparison seeing that there are no pockets that could trap air.

I have had 2 cars e-coated now (a 1957 Porsche speedster and a 1957 Austin Healey) and I can say that is the way to go if it is in the budget. I cannot see these cars rusting again unless they are involved in an accident and the coating gets compromised.