Welcome to the forum, John
 

Welcome to the forum, John.

It'll be great to have a person who knows paint inside.......and out. We all suffer from durability issues on repaints.........never is quite as good as the factory.

Repaints will never be as good as OEM. There are two basic reasons.

1) OEM materials are baked at 140C (285 F) Chemical reactions that occur at room temperature can never really be as reactive as materials cured with that much energy. Some of the coatings on MB's were two component like refinish urethanes, and still needed to be oven baked at high temperatures to develop full properties.

2) Remember the old musle car adage, "There aint no substitute for cubic inches"? I modified it in the paint industry to "There aint no subustitute for Mw." In other words, the larger the oligimers (parts that come together chemically to form a polymer), the more durable the coating. Ovens help one use larger starting pieces.

The increased reactivity at high temperatures makes a larger final polymer. Larger polymers apply better initially (Don't ask why, I could type forever on that subject. The explination is really stattistically driven.) and have better durability because the final product from the larger pieces is more durable. Refinish is always at a disadvantage. The idea is to apply in such a way to minumize the difference.

Nice to have you on board!

Your timing couldn't be any better, my SDL's paint is sun baked and I'm getting her sprayed this winter. I'm sure I'll have a bunch of questions after listening to the shops.

What year is the SDL? It'll give me an idea on the technology being used.

1987, they used Glasurit paint, but the drivers side and probably most of the rear were repainted at some point in the early 90's. Probably 1993-94ish. Whats happening is the roof, trunk lid, and rear quarter are turning white. The sun seems to have baked it out after all these years. Their is nothing left, buffing it doesn't really do much.

You did a nice job with Toyota. My moms 2007 Rav4 has a very nice paint job, its pretty hard to you have to try to chip it. No orange peel either. Its far better than the paint on my dads 07 Ford.

I clay the Toyota and throw on a couple of coats of Meguiars NXT a couple of times a year, looks great!

Silly me, it was on your post.

The car is electrocoated, but there is no galvanization.

When you paint, you want to make sure you do not disturb the first primer on the car if at all possible. That is the electrocoat or e-coat. That is the key to corrosion resistance on modern cars. It was a PPG invention, and those were the most valuable patents ever to exist in the paint industry. PPG cationic e-coat had a 96% market penetration at its height--the same as Windows on a PC. There is no refinish substitute for e-coat for corrosion protection.

When you prepare the surface. Try not to disturb the ecoat. Rust will increase dramatically if you do. Also, there are some very toxic heavy metals like lead in the ecoat. You do not want to breathe those in.

One thing that a lot of people make the mistake is sanding and prepping the car and leaving it outside. Big, big mistake. Ecoat cannot tolerate any UV. None at all. Not even a couple of hours. E-coat manufacturers have very stringent UV transmission standards for topcoats. Maximum allowable UV transmittance specs are written into the contract. If there is delamination of a coating off of e-coat, the first test the e-coat manufacturer does is a UV transmission test on the topcoat. If that fails (too much UV goes through the topcoat), then the e-coat's warrenty is voided, and the auto company is responsible for the failure. I've seen e-coated car bodies left out by the manfuacturer chaulk in 8 hours in the sun.

The only way you can fix UV damaged e-coat is to remove it. Sometimes you have to remove all of it.

I've found the most successful repaints disturb the original coatings as little as possible.

Glasurit is of course BASF's trademark, and like most suppliers, have a full range of technologies. Do you know if it was a 2k urethane or a laqquer? I'm assuming it is a clearcoat since the Germans clearcoat all colors (non metalics on Japanese cars are monocoat).

Again, my last post applies. If you can leave the e-coat intact, things are much better. I would just prep the car w/o removing more of the finish than you need to. Spray it with 2k urethane coatings. It should look good for a long time. Glasurit's good, PPG's good, Dupont's good. Herberts used to be the best. I used to compete against them in Europe before they were bought out by Dupont. They knew some stuff that I couldn't match. I later learned their secret at SW. They used to have a joint venture with SW and some of their propiertary equipment was in SW's auto plant outside of Lexington, KY to make their coatings for the US market. The SW people kept saying how hard it was to use and it didn't work any better. The design was brilliant. I finally understood how they kept beating me technically in Europe. If Dupont hasn't just kept the name and crossfilled their stuff into the can (at least in the US), then that was the best at the time.

If you use a waterborne basecoat, make sure you or the bodyshop mixes the isocyanate in. It will dry and look ok if they or you don't, but the properties will not develop w/o the isocyanate.

I *think* from the factory it was a very not environmentally friendly laqquer without a clear coat.

I could be wrong, I need to do a little research.

In the US, BASF used the Glasurit trademark only for their refinish. The OEM materials simply went by BASF. So when you are talking about Gasurit finish on your Benz, are you talking about the OEM finish or a repaint? If it is a repaint, that finish you can totally sacrifice w/o losing anything. If it is the OEM finish, then you want to be more careful.

The chemistries of most OEM finishes are acid catalyzed, melamime acrylic based coatings. DB and BMW usually used 2k iso/melamine or just iso curing clears that required oven baking. It was a very complex clear application system, but the final product was superior. Low solids (lots of solvent in the supplied paint) allowed for larger starting materials (larger Mw as I talked about earlier), which provided for superior appearance and durability.

In Germany, there were not significant limits on VOC amounts in the '80's, but there were specific solvents you could not use to reduce the coatings. This was the same in England at the time. It was easier and cheaper to provide a quality finish w/o the VOC restrictions. You can actually tell in the early '90's when the Germans started lowering the allowed amount of solvent in their coatings: the appearance lowered significantly when compared to Japanese cars of the same vintage. It wasn't a cost reduction, it was the physical chemistry of applying high Mw versus a lower Mw of the starting materials. "There aint no substitute for Mw."

The goal is still to preserve as much of the original coating under the refinish as possible. In the OEM world: Herberts was the best. Nippon and Kansai could produce high quality, polluting paints, but their quality was very poor when they had to deal with enviromental regs of any kind. PPG and Dupont and their strengths and weaknesses. The technologies were roughly equivalent. BASF was always the worst OEM supplier. I remember taking a train from Prague to Berlin in '91. I happened to sit with a Skoda (owned by VW at that time) paint shop chemist. We talked about the different manufacturers, and she confirmed tha BASF was the weakest supplier in Europe as in the US. They are a much better refinsish suppler than OEM supplier.

Hope this isn't too much info, but it gives you the big picture on auto coatings.

Interesting, I am going by Glasurit for factory because it has the little G in the paint code on the front crossmember. But I might be wrong.

Either way it sounds like the goal is to keep as much of the original paint intact as possible. IE light skuff, no crazy sanding.

For a good quality after market finish, would you recomend sticking with Glasurit ot maybe going to another brand? My friend did his E300D in DuPont and it came out pretty good.

Bill, this is my last question, after this well move it to the proper forum.

To answer your question for the base/clear:

Any good manufacturer will work: PPG, Dupont, BASF Glasurit.

Stay away from laqquers. Easy to apply but no crosslinking to build properties.

for primer surfacers use Ditzler DP 40 epoxy primer. It really is the best. It worked so well that the refinish formula was the OEM primer for Corvettes for years (and the plant manager hated PPG! He could sub it though!) They placed total abatement (caught and destroyed all organic vapors emitting from coating) at the plant so they could use this stuff.

They may have found a compliant replacement by now, but that is how it stood when I was painting cars in the factories.

Yes, the biggest mistake made is to remove all the original finish. There are only two times you need to do it.

The coating is totally destroyed.

Something is seriously wrong with one of the coatings. Either the coating is delaminating, or nothing will stick to it, and the refinish delaminates.

Usually that is only a problem with GM's and Fords, (long story: don't feel like typing that all out) but it is possible to get an overbaked car. (Guys went to lunch, stopped the paint line, car was accidently left in the front of the oven for an hour, car then got another 30 minutes of baking when the line starts, car comes out with overcured paint that nothing will stick to and the finish tends to crack. Worst case: car left in oven overnight or over the weekend--you get the picture.)

You never know what you'll run into, but Mercedes' booths were very well run in the '80's.

Hi, John.

If the original coating needs to be removed because it is destroyed, what should you use to replace it for, say, welded in sheet metal?

Thanks,
Mark

Just being the devils advocate here,,,, on the E-coat deal. We routinely get factory panels with E-coat that has runs, DA scratches, or other imperfections that requires sanding through the E-coat to the bare metal. There goes the E-coat. We put an epoxy etch primer on the panel and move on. I have never had a problem with a come back over that procedure and wonder if the E-coat thing may be overhyped ? On the OEM over the aftermarket refinish, I always believed that the aftermarket was superior due to the fact that we can still use products that the factories can't any more. I have seen finishes we have done over 20 years ago still holding up quite well,,, something that a 20 year old OEM finish can very rarely say. I always heard that the plain chemical linking was as good as the baked linking, as the baking just tended to hurry the process. This is in no means a rebuke, just what I was taught.

Thats funny you said that. My parents had a astro van that had bad paint on the hood. It looked like the paint started to crack into star like shapes all over the hood and top of the car.

I asked this on another thread, but will ask here, too. Is there anything new with auto paints where a combination of the paint chemistry and some other external treatment will produce a finish more like the factory, baked-on finish? Ultrasonic, infrared, electrical charges?