Clear coat chipping, best prevention

6

6T1

Saw this question on another forum, what is best clear to prevent this?
 
I read the link you sent me and I appreciate you not posting it, as what is written on other forums is really none of my business but there is a lot of bad info posted there.
This is not a short easy answer but I will over the next day or so make some posts about this but will take me some time.
 
Let start with the undercoats as its all related as to how well a paint holds up to stone chipping.
Big contributors as far as undercoats:
Trapped solvents.
Use of cheap 2K primers.
2K primers sanded and then setting to long without resanding.
Use of lacquer primers.
Improper use of time windows for 2K sealers and or 2K primers when using as a sealer.
Using adhesion promoter over e-coated parts or sanded primer.
Improper flashing of first coat of base.
Dry spraying first coat of base.
Using to fast reducer in base for the temperature you are spraying.
Base not setting long enough when done with last coat, before applying clear.

This is a start, will do more soon.
 
Part 2.


Best undercoating procedures.
Epoxy
2k primer with proper flash and proper sanding.
Epoxy as a final sealer, nothing is as good as epoxy as a sealer due to its adhesion and the base adhesion to the epoxy, this is why almost every restoration shop uses epoxy as a sealer but production shops cannot wait the extra time to use it, so they will use a 2K urethane sealer. However over the years I have seen a lot of production type shops go to the epoxy as a sealer on “front end work” because of the stone chipping problems they have had.

Clear stone chipping causes.
Dry spraying first coat.
Using a production spot repair clear.
Acrylic urethane clears.
A clear without much flex (aka) spot repair and fast dry clears.
Too hard of a clear.
Trapped solvent in first coat of clear being not enough flash time or using to fast activator
for the room temp. Fast is not always faster.
Using too many coats of a production type clear, most of these clears advise against more the three coat for stone chipping problems.

Nanos, has nothing to do with nothing and totally false on the info given.
I just counted we have thirteen (there are 100’s if not more) different nanos in the plant and each one does a different thing. We use then in epoxy, 2K primers, 2k sealers and have done extensive testing of different ones in clears and single stage paint going back to 2007.

Next post clear.
 
What clears are best?

The answer is as cut and dried as they come, a Polyurethane clear.
All the normal production clears made by the majors are medium to low solids medium acrylic urethanes. Thinner and harder equals faster for production work and most are two coats and deliver with some recommending three coats to get proper mils.
One major spot repair clear you all know and has been out for years, used by many production shops, formula was changed a number of times and name a couple of times, now discontinued, reason? Cars would be repaired and if the guy drove on a gravel road or drove on expressway to work, the car would come back looking like it had been sandblasted in 6-12 months, clear had no flex but it was fast and easy to use for those insurance repairs.

Acrylic and polyurethanes are points people like to argue about if there is a difference but there is a big difference as far as the amount of coats you can apply without losing the durability of the clear, more chemical resistance and almost always higher solids.
Higher solids mean more ISO’s to kick to compensate for the extra polyol and get the proper OH/NCO ratio and the ISO’s them selves add more durability and chemical resistance to the clear.
If this is wrong, then why does every skydrol approved clear for aviation , has the name Polyurethane on it?
Why is the most expensive and best clears from the majors, Polyurethane?7800 Glamour clear until replaced with 7900 that failed.
2002 PPG mainstay for years.
These clears have the flexibility and the softness to give you the best stone chip protection IF you have prepped the car the right way as discussed earlier.

Also I did forget in previous post to list activating the base as one of the best things you can do, to help prevent chipping.

Hopes this helps as a book could be written but I tried to just make key points, so you know, chips have more to do with how everything is done, not just what clear you used.
 
If you ever decide to write a book, let me know. I'll be first in line to buy it!

I read a ton of books trying to learn about new things, and most of the auto body books are lacking the technical info I love.
 
mitch_04;32875 said:
If you ever decide to write a book, let me know. I'll be first in line to buy it!

I read a ton of books trying to learn about new things, and most of the auto body books are lacking the technical info I love.

You will never need to worry about me writing a book!!!! Still trying to figure out what a full sentence is!
 
This is awesome info. The type of info I need to help sell the product. Now just explain the differences in 2K primers.
 
Kroozen, hang around and learn this stuff inside and out and you'll sell a lot of product.
 
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