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Robos911

How to respray a 911!?!

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50 minutes ago, Robos911 said:

and i can spray epoxy undercoat (no isocyanides) with Celulose over the top so im thinking of doing this, anyone tried it?

Inter-coat adhesion is critical for a quality finish.

Solvent systems like cellulose melt/dissolve together at the interface of each coat giving a very strong physical bond. They do not have a lot of adhesion and/or chemical bonding.

This obviously can't happen on the first coat, hence etch primer which chemically bonds to the metal, together with some adhesion. Subsequent coats "melt" together. So the whole thing is a proven system.

Chemically cured products (epoxy, 2K, etc.) Are designed to stick to each other by mainly chemical bonding with some adhesion. 

I get away with solvent based clear coat over water base because the solvent does melt the dry water based coating. The water based coating is also designed to both chemically and physically bond with any primer type so it can be used in patch repairs on all cars as well as full resprays.

I would stick to proven systems.

Mark

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Why dont you just get a air fed mask and use 2k ? 

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I'm not a pro but I researched this and concluded 2k is more risky heath wise, less forgiving application wise and less durable Vs the improved UV resistance and hardness of the modern lacquers. Happy to be challenged. But completely agree with SilverWT

Sent from my Pixel 2 XL using Tapatalk

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48 minutes ago, Henry said:

Something like this would do . You can then use normal 2k probably cheaper easier to apply .      https://www.spraygunsdirect.co.uk/index.php/masks/airfedmasks/devilbiss-vizi-601-air-fed-visor-outfit.html#sthash.xic8B5Bz.dpbs

Spraying 2k would make me nervous and the proper kit (in your link) with the Air line filters is nearly £450 + i would probably need a bigger compressor!!  If it gets to that i would pay somebody else....

1 hour ago, SilverWT said:

Inter-coat adhesion is critical for a quality finish.

Solvent systems like cellulose melt/dissolve together at the interface of each coat giving a very strong physical bond. They do not have a lot of adhesion and/or chemical bonding.

This obviously can't happen on the first coat, hence etch primer which chemically bonds to the metal, together with some adhesion. Subsequent coats "melt" together. So the whole thing is a proven system.

Chemically cured products (epoxy, 2K, etc.) Are designed to stick to each other by mainly chemical bonding with some adhesion. 

I get away with solvent based clear coat over water base because the solvent does melt the dry water based coating. The water based coating is also designed to both chemically and physically bond with any primer type so it can be used in patch repairs on all cars as well as full resprays.

I would stick to proven systems.

Mark

Yeh, im thinking cellulose but ive heard good things about epoxy and the website (rustbuster) says suitable for cellulose??

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Hi There,

That's the mask that for spraying 2K which works really well. You do need to remember though that all the mask does is get the air  to your face, you need to ensure the compressor feeding it has a clean air supply. The compressed air then needs to go through a 3 stage filter(£300 ish) to get the compressor oil etc out of it before you can breath it safely.

The mask does use a lot of air, for spraying a single panel I can get away with a single 3ph compressor but for doing anything bigger I use a pair of 50 litre 3 hp compressors linked together.

Getting the water out the air something you also need to do for a decent finish, a dryer was expensive last time I looked but I have a 10 meter run of copper pipe  with drain off points that works well. 

I must admit the setup is a  hassle but  the  finish and durability of 2K is amazing, I tend to use the following paint process for clear over base metallic :

  • Prime with 2K epoxy primer(Lechler).
  • Apply any filler required(UPOL Fantastic).
  • Flat
  • 2K epoxy primer again.
  • 2K Spray filler(Lechler Green Ti)
  • Flat `
  • 2K epoxy primer again.
  • 1K base Coat 50% Coverage
  • 1K base Coat 100% Coverage
  • 1K base Coat 25% Coverage
  • 2K Clear Coat 50% Coverage
  • 2K Clear Coat 100% Coverage
  • 2K Clear Coat 100% Coverage

 

Rich

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The lechler epoxy is good stuff , no need for etch primer these days in most cases , the rich zink content of the first coat provides good adeshion and is waterproof  protecting the steel . 

Thats exactly the paint system in that order that I have used in my last two resprays and will use again in a month on my MGA , also used it on my Triumph .   Certainly dont put the compressor in the same area as you are spraying in !

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I should add the reason im thinking the rustbuster epoxy primer is that im repairing the car in sections so parts will be in primer over winter and the respray wint be until next year.  Supposedly epoxy is completely waterproof and the only one that will prevent rust if left???

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1 hour ago, rich73 said:

Hi There,

That's the mask that for spraying 2K which works really well. You do need to remember though that all the mask does is get the air  to your face, you need to ensure the compressor feeding it has a clean air supply. The compressed air then needs to go through a 3 stage filter(£300 ish) to get the compressor oil etc out of it before you can breath it safely.

The mask does use a lot of air, for spraying a single panel I can get away with a single 3ph compressor but for doing anything bigger I use a pair of 50 litre 3 hp compressors linked together.

Getting the water out the air something you also need to do for a decent finish, a dryer was expensive last time I looked but I have a 10 meter run of copper pipe  with drain off points that works well. 

I must admit the setup is a  hassle but  the  finish and durability of 2K is amazing, I tend to use the following paint process for clear over base metallic :

  • Prime with 2K epoxy primer(Lechler).
  • Apply any filler required(UPOL Fantastic).
  • Flat
  • 2K epoxy primer again.
  • 2K Spray filler(Lechler Green Ti)
  • Flat `
  • 2K epoxy primer again.
  • 1K base Coat 50% Coverage
  • 1K base Coat 100% Coverage
  • 1K base Coat 25% Coverage
  • 2K Clear Coat 50% Coverage
  • 2K Clear Coat 100% Coverage
  • 2K Clear Coat 100% Coverage

 

Rich

That sounds like a good set up, not sure for my first time out though!!  Also not sure if im doing a full respray in one or just the back end and scuttle.  Which is why im wondering what system Porsche wouldve used in 85??

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 Glasurit 21 line  2k,  you can still buy it ,  or equivalent possibly 54 line  but it more expensive than most , no real point in your case unless painting whole car . No real short cuts in painting if you want a quality result  .

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1 hour ago, Robos911 said:

Which is why im wondering what system Porsche wouldve used in 85??

Try a small area with solvent thinners on a cloth. If colour comes off it would have been a solvent based solid system (i.e. it hardens by evaporation of the solvent carrier and redissolves in solvent). If no colour comes off it is either a solvent clear coat, or a clear, or solid chemically cured system. Continued rubbing and careful observation will tell you which.

Edited by SilverWT

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Mark may be right about the solvent based solid , he often is ! 😉    Fairly sure they used Gasurit  but possibly otheres as well .  I painted my BM tii  polaris silver in 54 line early to mid nineties in my brothers then paint shop .

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On 11/13/2019 at 8:02 PM, SilverWT said:

Try a small area with solvent thinners on a cloth. If colour comes off it would have been a solvent based solid system (i.e. it hardens by evaporation of the solvent carrier and redissolves in solvent). If no colour comes off it is either a solvent clear coat, or a clear, or solid chemically cured system. Continued rubbing and careful observation will tell you which.

Well the answer seems to be a be a bit of everything!!

The celly thinners removes paint where i know its original, so inner frunk and under dash. F1EDF6F6-924E-48A3-816D-24DA190DA97F.thumb.jpeg.6b1c437a6125fb8031041f4b793de997.jpeg


CB8AA4A5-11BB-4890-922D-68640DAFE47B.thumb.jpeg.67de551f0a7f7094aa42eb716baadf05.jpeg
 

but on the external panels no paint comes off!

98EB6192-5247-4E64-A4B0-53C1D847FB96.thumb.jpeg.4c094cdd8550cf400ae66f39c3918b59.jpeg

There is no lacquer on the outer panels (polishes colour off) so it left the factory finished in Cellulose but most of it has been resprayed in something else???

If Cellulose was good enough for Porsche its good enough for me👍
 

So thoughts now are epoxy primer (so i can leave the full spray until summer) celly primer, high build then top coat....??

Thanks again all, thoughts??

9AB5C57E-F5BA-4168-BECE-DC7ACC7E8CB0.thumb.jpeg.47eba70fa7691ed541796c7c95bc0e81.jpeg

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Don't use cellulose primer unless you are top coating immediately - it sucks up moisture from the air.  Epoxy primer is best if you need to protect the base metal and need further metal work or just won't be top-coating for a while.  Epoxy won't stick over etch primer, so avoid that.  Rust Buster epoxy stuff (121 for underbody and 421 for topsides) seems to work well (but I've only had it on since last winter, so time will tell).  When temperatures are down at current levels, the epoxy doesn't want to leave the gun.  Don't thin more than 15% (20% max.) & make sure the component cans are as warm as possible (ideally 20-25'C) before mixing & spraying,

Down the road, when you're ready, you can choose the filler primer, sealer (more 431 ?) and top coat system as epoxy primer works for all.

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14 hours ago, PeterK said:

Don't use cellulose primer unless you are top coating immediately - it sucks up moisture from the air.  Epoxy primer is best if you need to protect the base metal and need further metal work or just won't be top-coating for a while.  Epoxy won't stick over etch primer, so avoid that.  Rust Buster epoxy stuff (121 for underbody and 421 for topsides) seems to work well (but I've only had it on since last winter, so time will tell).  When temperatures are down at current levels, the epoxy doesn't want to leave the gun.  Don't thin more than 15% (20% max.) & make sure the component cans are as warm as possible (ideally 20-25'C) before mixing & spraying,

Down the road, when you're ready, you can choose the filler primer, sealer (more 431 ?) and top coat system as epoxy primer works for all.

Ive used the 121 on the underside, just brushed on, it seems pretty decent stuff, not great finish but fine for underneath. Only just realised 121 & 421 is the mixing ratio !! 
The 421 i might even brush if its too cold for spraying i can always flat it back when the weather is better!

Im thinking that the whole car will probably get a coat of celly in the summer now, then i know its all the same. So a bit of sanding/ prep to do!
 

Thanks!

Edited by Robos911

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19 hours ago, Robos911 said:

There is no lacquer on the outer panels (polishes colour off) so it left the factory finished in Cellulose but most of it has been resprayed in something else??? 

Seems unlikely they would have used different top coat systems underneath and on top, so most likely 1K solvent system originally with a 2K system respray at some point.

You can always give it a light coat of the final colour top coat to just make the primer moisture proof. Will then act as a guide coat when you prep for final finish.

Mark

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52 minutes ago, SilverWT said:

Seems unlikely they would have used different top coat systems underneath and on top, so most likely 1K solvent system originally with a 2K system respray at some point.

You can always give it a light coat of the final colour top coat to just make the primer moisture proof. Will then act as a guide coat when you prep for final finish.

Mark

Im Fairly confident the outer panels have all been resprayed!! Badly the inner panels ate original paint!

7B4CA9C9-34D4-43A7-8EA4-414C1860E2A4.thumb.png.6e517ddaca24f44bbda8551d3d9031a3.pngE3D28609-1637-4E0E-975C-8B38D2959CFF.thumb.png.1e0220f4a938f6b8a0d9b7f1147317b3.png
 

Bit of a mess really😂😂

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Might be worth looking at isocyanate free 2k.  I tried it recently on a single white panel and although it took several days to harden the finish was pretty good. I brought it on line from Jawel. 

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On 11/13/2019 at 4:14 PM, osc911 said:

I'm not a pro but I researched this and concluded 2k is more risky heath wise, less forgiving application wise and less durable Vs the improved UV resistance and hardness of the modern lacquers. Happy to be challenged. But completely agree with SilverWT

Sent from my Pixel 2 XL using Tapatalk
 

Just flicking through this.yes, 2k does have nasty stuff in it.However,Ive been in body game for nearly 30 years.Never met a painter who uses an air fed system.I use one if im doing a full paint.However,its more for eye protection than anything.The only guy I know who has suffered from ill effects, was a signwriter.The kind who used to stand on a ladder "Rosies florist" type stuff.Long before Vinyl cutting was a thing.A good quality mask should protect you Ok.Think 3M.If you choose to go air fed, your gonna need at least 15cfm compressor with a 150 litre tank.They are very demanding.

If your winging your paintwork, celly is far more forgiving.However for best results, youll need to wet flat between coats (1000 grit) 2 coats of solid 2k, and as long as you dont get huge runs, and a bit of gloss you can get a great finish if your prepared to work on it.2k is the most durable finish you can get, whether solid or base & clear.The base can be over painted in 2k, celly or acrylic.Again 2k & acrylic are more forgiving, but require more work.Porsche factory finishes have always been quality.Never seen an early car with factory "orange peel" yet plenty of new BMWs etc have terrible peel.

Who ever said "leave the factory underseal" was just swerving.Ive just spent two weeks stripping a shell & Panels.The thick seal made by Wurth is just a series of cavities to trap moisture.

Even in areas under what appeared to be undamaged, areas of rust were forming.It has to go.Bead blasting wont touch generally touch it either.if it does it will take an age,and cost too.

Torch & scraper, then zip wheel.Then media clean.

If you want a great paint job do this.Remove parts and strip everything.Strip paint with aircraft stripper,then on solid areas that are difficult to acess,get the area blasted.Ive just had 2 doors, pair rear & front wings and few odds blasted in hard to acess areas (after stripping) was charged an hour,£80.

THEN give all the parts shell if you have to, a decent painter.Youll be suprised how much you can save doing the hard work first.Dont apply paint of ANY kind.One thing painters dont like, is to paint parts that they havent prepped!

 

late 001.JPG

late 012.JPG

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Notice you can see the rusted areas,that were under the underseal.The front pan hasnt been cleaned,as its being cut off.Notice the "matt" area on the headlight bowls, where they were blasted.Sorry about double post.Cant remove?

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