15 replies to this topic

[psychobob]

I need to do a few small localised repairs on my hornet. it was repainted just before I bought it about five years ago, but has since developed a few small scabby patches, all of which seem to be just surface. I cant afford to have the entire car resprayed at the moment but i'm hoping to repair and respray each small section and paint with colour match aerosols for the moment. by the time I'm done, I hope to have the whole car blown over with the original paint. the plan is to flapwheel down to clean metal then treat it with rust killer. after that do I acid etch prime before filling or after? also is it better to use acid etch or zinc rich primer on bare metal? i'm guessing the order after filling and smoothing should be zinc rich primer then high build primer then coats of top coat, all lightly sanded between coats? also what colour primer should be under Maroon B paint? sorry for so many questions, i'm a bit of a newby to paint.

[cal844]

Dont flap wheel it!!

[sonikk4]

You can flap wheel the areas of rust but use a fine grit wheel ( this will depend on the size of the rust patch) Don't go mad though as the metal is thin to start with. So if you have a speed adjustable grinder then slow it right down. However if the metal is pitted then DO NOT grind the metal till the pitting has gone. You will more than likely go through.

If it is pitted then think about using a twisted wire cup on your grinder then a quick flash over with the flap wheel. Then if all is good treat the affected area then fill. Don't etch prime then apply filler. The filler really needs the bare metal suitably keyed to adhere to. If you have one use a DA sander either pneumatic or electric to sand the filler back. If not then do it by hand using a flexible block and wet and dry.

Any other areas of bare metal then etch prime, filler prime, flat back, prime, flat back then topcoat.

Now a lot of the above does depend on the tooling you have to hand. Personally I would use a pneumatic high speed die grinder with a medium roloc disc. Then a whizz over with the twisted wire cup ( for any deeper rust) followed by a DA sander. But again that is because I own a decent sized compressor.

[Daz1968]

Small areas can be done with a spot blaster if you have a compressor, think about epoxy primer as it adheres to bare metal and you can use filler over this and it completely seals the metal. Just remember to treat both sides if possible to ensure repair lasts.
Try to find out what type of paint is on the car before buying any top coat to minimise any problems. For high build primer the upol high 5 isn't to bad, just apply light coats as it's thinner content is high and reacts if you try to apply a thick coat, but it does sand well.

[Coxie]

Don't know if anyone else uses this but after removing small areas of surface rust I had pitting in various places on my project and was going to lead load them but got advised by a guy that restored old cars to use jb weld epoxy.
Bloody marvellous stuff

[psychobob]

im taking it I should be using acid etch instead of zinc rich primer then?. thanks for the advice though chaps.

[sonikk4]

Zinc rich primer is normally used on the welded joints. Etch primer is designed to eat into bare metal to give decent adhesion before the other coats go on. But saying that if you use both etch and Zinc rich together I can't see that being a problem.

Epoxy primer is supposed to be really good as it is not porous unlike other primers. Never used it yet but quite a few members on here rate it especially if you are not going to apply topcoat for sometime.

Going on from what Coxie gas said, the bodyshop where we had my lads car painted used to use fibreglass resin only over small areas of rust. Then once flatted back it was on with primer and paint. The old lad Ray recommended using this instead of filler. He did have 50 years of experience under his belt.

[Coxie]

I bare metalled and epoxied the roof of my project and it has come out flawless with no issues.
The rest of the car was done in a good quality high build and polyester filled any minor wobbles and the shrinkage I'm getting in places is driving me mad and that was after letting all the filled areas cure for 6 weeks.
That's the only thing with any pe resins is that they never stop curing and shrinking.
If I could do it again the whole car would get epoxy filled and primed.

[Stu.]

Zinc rich primer is normally used on the welded joints. Etch primer is designed to eat into bare metal to give decent adhesion before the other coats go on. But saying that if you use both etch and Zinc rich together I can't see that being a problem.
Epoxy primer is supposed to be really good as it is not porous unlike other primers. Never used it yet but quite a few members on here rate it especially if you are not going to apply topcoat for sometime.
Going on from what Coxie gas said, the bodyshop where we had my lads car painted used to use fibreglass resin only over small areas of rust. Then once flatted back it was on with primer and paint. The old lad Ray recommended using this instead of filler. He did have 50 years of experience under his belt.

Neil, Could I ask what you do on yours to protect repaired areas when, as you say, you wont be priming and topcoating for a long while. Im just about ready to start mine and I suppose this is situation for everyone doing a home resto without full workshop gear. I dont want to use epoxy as Im put off by 2K spraying at home. If you only used zinc, etch and filler primer, did you encouner any problems before, during or after topcoat (apart from the yellow Halfords reaction issues you had). Very many thanks in advance, and sorry for butting in on your post Psychobob.

[sonikk4]

At the moment I use zinc rich primer in the joints. The undersurface of the outer sill is painted as have the inner sill sections covered by the outer. With the car on the spit I then force more paint into the cavity as far as possible.

I'm looking into epoxy primer now and whether I can get this in aerosol form rather than having to apply it by spray gun.

As a temporary measure any external surface that's going to be left gets a flash over or a generic topcoat. This will then be removed prior to paint.

[Daz1968]

2k epoxy doesn't need airfed mask, think a2 p2 is listed as requirement on data sheet, look on rust.co.uk at the epoxy on there. You can also roller it on for protection before spraying the car. Not used it myself yet but will do on next one.
On my correct project I used upol acid 8 on any bare metal followed by high build 2k primer then 2k direct gloss. Underside I used zinc rich primer stone chip then 2k gloss. But I have set up with an airfed mask and wouldn't work without one.

Edited by Daz1968, 01 June 2014 - 09:35 PM.

[Stu.]

Thanks Daz. Ive had a good look at the sites epoxy primer and I think I'll give it a go. It should seal the work as you go to prevent moisture ingress and also says it can be filled over and applied over filler (with correct keying). I have a 1/2 respirator but will need to get the compatible filters as the ones I have dont meet A2 P2/3 spec requirement.

So I am thinking of trying this -

Body panels external.

Remove new panel etch primer if poor quality.
Upol etchweld to seams and welded flanges.
Upol acid 8 etch over bare metal.
Smooth / key old celly paint.
Upol fantastic filler to panels (larger dings removed by dolly & hammer).
Overcoat with epoxy primer 2 coats flatting back first coat.
Leave nicely sealed until ready for celly hi build primers, guide coats, fillers, stoppers and celly top coats.


Body panels internal / under floor.

Upol Etchweld to seams and welded flanges etc.
Prep / key old paint
Zinc primer 2 coats.
Seam sealer.
Epoxy primer 2 coats.
Stonechip.
Celly top coat 2-3 coats.

Knowing I can epoxy prime seal the body and not worry about moisture ingress until topcoating is great. The Upol filler says it can be filled over well keyed 180 grit old paint and can be overpainted with 'most paint systems'.

Do you think this looks ok bearing in mind I'll be filler priming and topcoating in celly ?

[Daz1968]

If you want to top coat with cellulose why not use 2k epoxy high build as it has less chance of sinking than cellulose.

[Stu.]

I'll be homespraying without an airfed mask and neighbours / pets on both sides Daz so really want to avoid proper 2k primers or topcoats The epoxy primers ok though as you say its not such a risk as 2k as long as you have a suitable filtered mask.

[Daz1968]

2k epoxy is not isocyanate so a good filter mask and good ventilation is all the safety sheet calls for, do a search for hb body 989 4:1 epoxy primer and read the sheets, only continuous exposure calls for supplied air,
It can be applied over bare metal and old paint so wouldn't need an etch primer

Edited by Daz1968, 02 June 2014 - 10:01 PM.