Time to Repaint?, Soda Blast?, Powder Coat?

[Coral Red Syd]

Searched the forums and did not find these answers.
So I need to be schooled on this topic if you would.

1984 Targa, I assume is galvanized.
Has clear coat peeling and assumed original paint is peeling in certain places under the hood. Under the peeling is a yellow cream color I assume is primer.
Car has no rust but a couple of door dings and such.
I want to do the best job on this car, so if I have to take it down to the frame for prep and painting that is OK.
Question: When should you have the frame soda blasted or are there an options for just repainting and clear coating.
Can you do soda blasting at home at a DIY - don't think so as I've seen mobile soda blasters of large scale only.
Will soda blasting hurt the galvinization.
Can you repaint certain areas or is it best to frame off and prep down to the metal. What about powdercoating the frame?

As you can see, I need a little schooling on the painting process... any direction appreciated.
Cheers
CRS

[Jeff Hail]

Originally posted by Coral Red Syd
Searched the forums and did not find these answers.
So I need to be schooled on this topic if you would.

1984 Targa, I assume is galvanized.
Has clear coat peeling and assumed original paint is peeling in certain places under the hood. Under the peeling is a yellow cream color I assume is primer.
Car has no rust but a couple of door dings and such.
I want to do the best job on this car, so if I have to take it down to the frame for prep and painting that is OK.
Question: When should you have the frame soda blasted or are there an options for just repainting and clear coating.
Can you do soda blasting at home at a DIY - don't think so as I've seen mobile soda blasters of large scale only.
Will soda blasting hurt the galvinization.
Can you repaint certain areas or is it best to frame off and prep down to the metal. What about powdercoating the frame?

As you can see, I need a little schooling on the painting process... any direction appreciated.
Cheers
CRS

My response is only a guide based on experience. Any "blueprint plan" for a restoration or refinishing project can only be based on the pre-existing condition of the vehicle and the end result expectation. Without seeing it in person I can only provide an educated guestimate.

The entire unibody sheetmetal is not galvanized (per se). Specific lower body components are prior to welding and Elpo coatings applied (E-coat) or ( Electro Paint Depositsion and Anodic, or Cathodic) to entire vehicle from the factory after a Zinc bath.

The original coatings done in the 80's were good unlike the nitrocellulose and lacquers of the 70's,60's and older year vehicles. So if you are not experiencing any delamination of the (Elpo)E-coat, base primer or sealers, do not have much rust you can use them as a base. Repair your rust and nuetralize,repair dents, machine sand the original clear and color coats down to the substrate coatings, re-seal, or prime, block and apply color/clear. There are more steps involved so I am simply outlining the basic repair plan.

Rule of thumb is the oem substrate coating are usually tough to beat. If they are in good condition use them as a base. Existing paint film thickness is a factor since if too thick or a prior repaint will create problems later.

If you have areas of lifting, checking or cracking then the problems are below the top coats. If the substrate coatings are damaged from age, UV, delam, poor adhesion, brittle, prior repairs or refinishing then stripping is the right way to procede .The decision to machine strip, chemical strip or media strip is dependant on the owner, complexity of the repair (budget, shop versus home repair) etc.

A DIY repair will lack re-application of the original (Elpo) E-coatings because of the process and equipment involved. In fact 99.99999% of bodyshops are not equipped to perform oem (Elpo) coating applications but use epoxy sealers and metal etching primers in place of when coating bare metal.

To take a step backwards on our soda blasting questions. Yes it can be done at home but I do not recommend it. It is messy if you do not have a containment area (blasting booth) that is big enough for a shell to fit in. Recycling the already used media unless you stop, collect and sweep up to refill the hopper is an issue. It is not cost effective for a one time use. Your neighbors will hate you if you do not have a containment area. Best to leave media blasting for big projects to the pro shops. Media blasting is an option dependant on how bad the existing metal condition may be. Other options exist such as acid dipping which are effective and thorough.

Powder Coating an entire car is not recommended. It can be done. I have seen entire interior sheetmetal PC'd succesfully.

The end result of any refinishing project or restoration is the materials used, the hands that do the work and the preparation done before any color is applied.

Have a qualified reputable bodyshop or painter take a look and guide you if you are unsure. Ask questions.

This is an endless subject and I am sure more will chime in.

[Buckterrier]

E-Coat, (electrodeposition), on automoblies from the 70's on is cathodic. It was a major improvment over anodics. In laymans terms, during the anodic process oxygen is released, hense less corrosion resistance. During the cathodic process hydrogen is released, better corrosion resistance. It is a 'paint bath' litterally were the frame, and body are dipped into the bath and the paint is electrically bonded to the substrate then baked.
Any paint can be applied electrostaticly, meaning a charge is given to the paint to attract to the substrate, as long as the substrate is conductive. This method is used for better transfer effiecencey.
As for powder coating class 'A' surfaces, I wouldn't recommend it either. You can't really get a superior finish especially the basecoat from it. Although H-D and BMW do use it for the clearcoat. Harley also uses powder for their frames. But again they are zinc phosphated prior to.
I agree with Jeff completely. Don't remove the 'factory' finish is you don't have to. No bodyshop can prep a car for corrosion resistance like an OEM finish. And yes ask a bazillion questions, here first if you're more comfortable with it. Post pics and good luck

[rennch]

This guy did a great series on stripping and prepping your 911 for paint. When I'm ready I'll probably go this route.

Paint Stripping 101

[Willem Fick]

I second emptyo on this. I followed the same procedure to do a complete bare-metal respray, and am extremely happy with the results. One thing that I did differently was to use a high pressure spray washer with soapy water to remove the paint (and remaining stripper) afterwards.

As for choice of paint:

If you want something that looks more period correct, it is probably best to go for single stage paint, whereas, if you want something that more resembles the paintjobs on new cars, you need to go with base/clear.

Given that your paint is already peeling, and you can see primer underneath, I would suggest that you give serious consideration to a bare-metal respray, as you may end up having your new paint surface marred by the sub-surface coming loose from the primer coat.

By doing a proper bare metal, it also gives you the opportunity to see any potential rust before it becomes a real problem. Rust has this funny knack to run under paint, and rot everything under it away without you even noticing.

Paint technology has come a long way from when our cars were built, and if you pay attention to detail, the end result will be far superior to whatever the state your car is in right now (unless of course it is a concourse queen!)

I documented my respray with lots of pictures - if you are interested, drop me a PM.

[rennch]

William,

I would LOVE to see your pics. You can send a link to porscheparts@whirledmedia.com if you feel so inclined.

Thanks!

Mike

[Coral Red Syd]

Here are the pics of where the paint is flecking and the clear is flecking. The hood is where the flecking is and the engine lid shows a fleck that was covered. The clear is flecking on the bumpers as shown. I was thinking of repair options for only the affected areas, however given the age of the car -1984- I was thinking of the full disassembly, soda blast, and repaint fearing that rust may be underlying... ? (do it once, do it right mentality...)
Also you can see where a radar detector was 'less' than professionally installed by drilling through the front bumper and a small section of the body by an installer when the car was new as per the original owner. Advice on repair of these is appreciated as well. One other thought, what color is this - how can I find out.
Thanks so much for the replies.
Cheers.
P.S. Got the right pics posted this time - ouch

[M.D. Holloway]

I asked this question last year and got mixed answers. I know a few guys who love the soda blast. The soda blast might need to be washed off which could lead to some problems. Bead blast seemed like the way to go. Some guys swear by ol fashoned sanding while others use a chemical strip.

Great question - hope we find agree