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paint chipping, why?

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  • Member since
    January, 2012
paint chipping, why?
Posted by All_6s_and_7s on Monday, June 11, 2018 10:22 AM

So This project I'm working on the paint seems to want to flake off or chip very easy. it has been dry for about 2 months and the finish is really weak.

I used all enamel paint, testor gold base, and I decanted the transparent blue from the testors spray bomb and used my air brush to paint the car.

The blue finish chips with the slightest touch of an object. The gold base and primer are not affected.

 Screenshot_20180611-111515 by David Phair, on Flickr

I like to work just as much as I don't.

  • Member since
    December, 2003
  • From: Nova Scotia
Posted by Bainford on Monday, June 11, 2018 1:28 PM

I was curious to read this post when I saw the title. I frequently have frustrating paint chipping issues, but it is always the paint chipping off of the primer.

I really don't know what the problem may be, but I have noticed that somemetallic paints like gold and silver will sometimes have a loose (almost dusty) finish when dry. This can be seen if masking tape is applied then removed again, some gold dust will pull up with the tape. It has ocurred to me at times that this 'loose' surface could affect paint adhesion when painting over with colour. Usually there are no issues, but on a couple of occassions I have masked over a candy red (applied over Testors gold base) and the tape pulled the colour up very easily.

Just putting that out there. I'll be watching to see if anyone has some solid advise.

Power matters in the straights.
Lightness matters everywhere. - Colin Chapman

Trevor

  • Member since
    January, 2012
Posted by All_6s_and_7s on Monday, June 11, 2018 1:46 PM

Thanks Bainford, that's a good starting point. I would have never have thought of that dusting. I have seen it when I spray some acrylics as it drys before it hit the surface.

I guess I am not get mechanical or chemical adhesion. If I were to lay a thicker base coat and wet sand the surface. What grit do you think would I use to at least achieve mechanical adhesion?

I like to work just as much as I don't.

  • Member since
    December, 2017
Posted by Dale Gribble on Monday, June 11, 2018 10:23 PM

All_6s_and_7s

Thanks Bainford, that's a good starting point. I would have never have thought of that dusting. I have seen it when I spray some acrylics as it drys before it hit the surface.

I guess I am not get mechanical or chemical adhesion. If I were to lay a thicker base coat and wet sand the surface. What grit do you think would I use to at least achieve mechanical adhesion?

 

 

i spent almost 20 years as an ICAR certified body tech ... Let me give you a few pointers ....

 

 

paint can be "too dry" for a second or subsequent coat . The chemical bond needs to still have an open film to bite in to. This applies mainly to basecoats as you need to get them overcoated and then top coated with clear in a quick succession. I'm guessing you let the gold fully cure before top coating, and I'm also guessing you used a gloss enamel , something with a shiny surface that didn't allow the kandy to bond properly .... Try a basecoat gold , I'm sure your problem will solve itself at that point as basecoat dries "flat" and gives enough tooth for the next coats to bind ...

 

 

second - NEVER EVER EVER sand a metallic finish that you are planing on shooting either a kandy or clear !!!! Only wet sand Metallics when topcoating with another coat of same color metallic . You WILL get sand scratches that will magnify under gloss or kandy coats. And don't sand the kandy layer either! It is dependent on even coats to achieve the miles deep color Kandy is known for . If you wetasand the Kandy , it will make it uneven and splotchy looking . Something you cannot recover from by adding more coats . 

"rare" kit? no such thing!

build it, dont let it sit on the shelf.....

you cant take it with you, hearses dont have luggage racks......

  • Member since
    January, 2012
Posted by All_6s_and_7s on Tuesday, June 12, 2018 7:21 AM

Thanks Dale. What is the time line that you would apply the candy? are we talking 20 mins after the base coat? could you suggest a better base coat brand or something you would use?

I have had some successful paint jobs with these candy colours and they look fantastic when I finish them, it's just the aftermath of handling them and having chips happen. It's something that I don't ever see with regular paint jobs.

I try to shoot my paint at a low air pressure, so as not to dry the paint before it hits the car and I shoot indoors, so temperature is always constant.

It was a beauitful job before disaster struck.

 20180429_191759 by David Phair, on Flickr

I like to work just as much as I don't.

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