New Body Panels Painting Questions.

He is quite correct. Any new panel should be flatted and primed before topcoating. It's been botched and they should redo it. A nice easy case in the small claims court if they don't.

"Tom Burton" gurgled happily, sounding much like they were saying:

He's bang-on the money.

"We'd be happy to do it for you, but you ought to get it done for free by the last bunch of muppets".

Sounds like this bunch are honest to me...

Yes. To make a proper job that paint should be totally removed and the whole panel treated as bare metal on both sides. Etch primed then painted in the usual way. Then wax treated on the underside if that's how it was originally.

Because few do this properly it's not unusual for replacement panels to rot through before the rest of the car.

Yes it does i had the same problem , i took mine back to the body shop , they inspected it and agreed the sprayer had not preped or primed , they redid the job , gave me a hire van whilst they soughted it and the sprayer got a p45 oh and they gave me a free full service

If the paint on the new panel as supplied is a good quality etching primer, as it should be, there's no need to remove it all back to bare metal. The easiest way to test is with cellulose thinners and if it comes off easily or flakes off if you rub it with a coin it needs to be removed but from a reputable supplier the paint should only need flatting, undercoating and then topcoating. I've sprayed a good few panels in my time and not found one that needed the black paint removing first.

I think you'd have to buy new panels from a real cowboy to find paint on it that was so useless it all had to be removed. They work to certain standards or go out of business pretty fast.

I'm not sure about Scotchbrite but perhaps that a new method. Scotchbrite can be fairly coarse and you wouldn't want to see scratches showing through the finished job. I'd be looking to remove any sags or runs with medium wet and dry and then give the whole panel a light flatting with 1000 or 1200 grit to provide a key for the undercoat. That should also then be flatted if necessary and wiped with a tackrag and thinners before topcoating.

Pinholes are usually due to grease or other contaminants on the substrate preventing the topcoat adhering properly. Just fingerprints can cause it quite easily if the sprayer has been careless. A wipe with thinners and a tackrag should prevent that ever happening.

You can get scotchbrites with grits sizes as high as 1500

I'd agree with that - but many I've seen just use some form of black or brown paint - and definitely not etched.

I discovered a few years ago that Scotchbrite is available in (at least) three different grades. The regular green stuff, but also grey and red. IIRC the grey has very fine abrasive coating - no chance of that showing through paint. I've used it to ''key'' primer and had success.

Julian.

Before we get too hung up on the scotchbrite stuff errrm,errrr, he errm, may well have said "like scotchbrite" wither way i think the point about abrading the surface stands.

Tom

This black (sometimes green or grey) primer is indeed a shelf primer, some manufactures use softer primers, whereas some use better quality, some panel makers stove the panels and some do not.

In my experience the better quality shelf primers don't wipe off with cellulose thinners, but the softer ones do.

The paint recommendation is to remove all the shelf primer and apply a proper auto-body primer, but this may not be always necessary.

Acid etching may give additional adhesion properties to steel however acid etching is more suited to give bare aluminium a better key.

If the primer is a suitable substrate ready for additional coats of primer then all you need to do is rub over with a Scotch-brite.

I would recommend the maroon grade for keying the primer ready for subsequent coat/s of primer.

Colour Coordinated for General Applications.

Dark grey Blending/finishing of stainless steel, weld blending

Brown Blending, deburring, weld cleaning, oxide removal, rust removal

Dark green Heavy duty cleaning, oxide removal

Light green Cleaning, equipment maintenance, blending, intermediate finishing

Maroon Fine finishing, cleaning, paint keying, light deburring, blending

Light grey Very fine finishing, light cleaning, die polishing, denibbing

White Light cleaning, will carry compounds very effectively.

Scotch-brite cloths should be available from decent paint factors.

Stephen.

That's why I was careful with the pruning - I wasn't commenting WRT the OP's predicament.

Julian.