Made a big mistake! Cellulose over oil based.

[SpitfireIV]

Hi all,

First time poster here, but long time lurker, sure learned a lot from the articles and forum questions, but, I have one of my own now that I hope someone can help me with.


I'm working on a MkIV Spitfire, total and utter rebuild from the ground up. Just yesterday, things going great I applied UPOL Gravitex to the underside of the tub, which, in no time at all began to lift the rust primer I had applied under it, little wrinkle here and there at first, gradually getting bigger until the stonechip and rust primer could be peeled off like a soggy, solventy tissue paper......damn.

Rookie mistake, the rust primer I used was oil based I believe (thins with spirits) and the Gravitex is cellulose based (strong stuff apparently and a bloody good paint stripper if nothing else!) The rust primer was applied in early Jan, I scuffed it up yesterday, cleaned and wife it down before applying the stonechip.


So, I've had to strip back the underside to metal and will take another approach having learned dearly my mistake.


Now, to my question, or, my concern. Over the past few months I've been carefully cleaning, treating and painting the interior of the tub, section by section; floorpans, boot, bulkhead etc etc. Treated with Deox Gel, then applied Hydrate 80 and then, once more I used this oil based rust primer to paint the lot, two coats in fact with seam sealing in between!

Oh oh! My plan is to use cellulose to paint the car; DIY job. Was planning on giving the inside a blast of primer and then the topcoat, but, obviously the primer is cellulose based and I fear A. all my work has been in vain and B. the inside of the car could resemble soggy tissue in no time!!!


Q. Will a bar coat applied over the oil based rust primer allow me to carry on then with the cellulose based or do I have to strip the whole lot back and go back to square 1?


Thanks for any help at all guys!

 

[penfold]

Now it's all off, why not go large and put epoxy primer on? It sticks like poo to a blanket.

 

[500e]

"Rookie mistake, the rust primer I used was oil based I believe (thins with spirits) and the Gravitex is cellulose based (strong stuff apparently and a bloody good paint stripper if nothing else!) The rust primer was applied in early Jan, I scuffed it up yesterday, cleaned and wife it down before applying the stone-chip".
How long have you been married

 

[steveo3002]

stonechip is the worst for this ...very heavy in solvent and thick so it sits there and soaks , you might get away with celly primer

i agree though roar it off , roar off the hydrate 80 and deal with any rust until its all gone then on with epoxy primer onto clean bare metal

you can still use celly top coat if you wish but the epoxy primer is way way stronger and sticks so much better than other products

 

[SpitfireIV]

How long have you been married

Well spotted, not married just yet

stonechip is the worst for this ...very heavy in solvent and thick so it sits there and soaks , you might get away with celly primer

i agree though roar it off , roar off the hydrate 80 and deal with any rust until its all gone then on with epoxy primer onto clean bare metal

you can still use celly top coat if you wish but the epoxy primer is way way stronger and sticks so much better than other products

The underside, prior to having the rust primer and hydrate 80 applied was cleaned back to bare metal and the rust removed, although, oddly enough, when peeling back off the solventy gloop yesterday I noticed a few little fresh patch of orange rust, all be they light, under the hydrate 80. The hydrate 80 is suppose to kill and prevent rust! Perhaps its just as well I had this little set back so....

I dont understand what UPOL mean by a 'suitably prepared surface' when applying the stonechip. For instance, would a zinc primer be classed as 'suitably prepared'? I'll look into the epoxy primer, would it be a case of applying a coat of epoxy primer, then stonechip, then base coat? ( I have some bottles of gravitex still and would like to overcoat this with the body color).


The inside though, thats going to be a PITA, even the thought of having to roar all that off I might chance my arm and try a bar coat and see what happens.....

 

[Rocketman]

The thinners in the gravitex melted the underlying coat that is all.

A much better way of doing what you have done is to use a epoxy primer before. Only use hydrate 80 on rust that you can't get off, though the best method is still to remove all rust. But even if you do use hydrate 80 you would still go over it with epoxy primer. BTW you can use a brush for epoxy primer under a car and by the time the gravitex is over the top you would even know you had used a brush for the epoxy.

Looking at the top coats on the gravitex. If they aren't going to be 2k but 1k acrylic or even worse 1k acrylic aerosol you may need to be careful still. While gravitex is a lot less susceptible to crows feet than some other stone chip finishes there is still a chance due to the high solvents that it would happen. If you wanted to avoid this I would tend to use a thin coat of epoxy primer instead of a barcoat over the gravitex.

 

[steveo3002]

rust convertors dont work in my experiance ,try a bit on some scrap and scratch it afterwards bet its still brown rust under it

if you remove all the scabs with deox gel or whatever means you see fit then its gone and thats that , nothing left needing any magic lotions to convert and no magic lotions to cause problems further along the line one day

i wouldnt waste time looking into zinc primers , epoxy is the way forward , its affordable and non iso in most (all?) cases so no real reason not to use it

 

[steveo3002]

anything thats not 2 part /2k relies on the solvent evaporating for it it to dry , thats why a sopping wet coat of solvent heavy stonchip sitting on top often softens it and casues agro

the 2 part primers go off via a chemical reaction much like the body filler im sure youve used , once its gone off its very resistant to solvent and petrol spills etc

 

[SpitfireIV]

Cheers guys! This paint business is head wrecking to say the least, but I'm learning a lot! Must throw up a few pictures!

One other thing, I do have a litre of Bilt Hamber Epoxy Mastic thats unused! I'm guessing I'd need a primer for that, it couldnt be applied direct to bare metal. I will be picking up etch primer for the body of the car, would a coat of etch primer on the underside act as a key for the epoxy mastic?

I'm taking a trip tomorrow to a paint suppliers where I hope to pick up all necesary materials and paint in one fowl swoop!

 

[steveo3002]

your not listening are you lol

epoxy straight onto bare metal..no etch , same for body and underside

make up your own paint system and you risk alsorts of troubles and scraping it all off again

 

[marlinspike]

From all I have read on here, the general view seems to be that epoxy primer is the way forward for car body work and better than using etch primer.

As I understand it you can put BH epoxy mastic over etch or epoxy primer.

By zinc primer are you thinking of BH Electrox? It is a great product - 90% zinc - but pretty expensive and if it is going over good clean metal I am not sure there is any great advantage to using it instead of epoxy primer. You can brush it on of course, but you can brush on certain epoxy primers too.

 

[optima21]

on one of my polos, I stripped it back to bare metal then brushed on 2 coats of bilt hamber zinc primer, then brushed on 3 coats on gravitex. 3 years later rust is showing though, so on my other polo, i used just 3 coats of jotun 87 epoxy mastic (on bare metal).......just need to wait a couple of years to see if it lasts longer.

 

[SpitfireIV]

your not listening are you lol

epoxy straight onto bare metal..no etch , same for body and underside

C'mon, I'm a complete newb, as has been demonstrated, this paint stuff is very confusing, you could ask 10 guys and get 20 different opinions, one guy swear by one method, another swears by a different one :P

Like the above, and below....

As I understand it you can put BH epoxy mastic over etch or epoxy primer.

By zinc primer are you thinking of BH Electrox? It is a great product - 90% zinc - but pretty expensive and if it is going over good clean metal I am not sure there is any great advantage to using it instead of epoxy primer. You can brush it on of course, but you can brush on certain epoxy primers too.

I was looking at the likes of Zinc182. Perhaps epoxy priming the whole shell could be the way to go. As I understand its: Epoxy prime -> onto filling/sanding stage -> apply a sealer of epoxy primer once again and then onto the high build.

on one of my polos, I stripped it back to bare metal then brushed on 2 coats of bilt hamber zinc primer, then brushed on 3 coats on gravitex. 3 years later rust is showing though, so on my other polo, i used just 3 coats of jotun 87 epoxy mastic (on bare metal).......just need to wait a couple of years to see if it lasts longer.

I'm dealing with a '71 British Leyland car, rust is never far away! :O

 

[steveo3002]

put it this way

etch and high build primer in either celly or 2k isnt wrong , its a well used way to paint a car

epoxy primer is a newer and more durable system thats better than the above

zinc182 and the like isnt something any pro shop would use to primer a car

 

[Rocketman]

Don't forget the seam sealer after the epoxy but before stone chip if you are doing stuff under the car.

Not sure they ever used seam sealer on Leyland cars , could be a new experience for the old beast
Did they not park the cars in the sea for a week before painting

 

[SpitfireIV]

Don't forget the seam sealer after the epoxy but before stone chip if you are doing stuff under the car.

Not sure they ever used seam sealer on Leyland cars , could be a new experience for the old beast
Did they not park the cars in the sea for a week before painting

I had all the underside seam sealed but I've had to rake it all back out with the old rust primer :/ Is Tiger Seal an appropriate seam sealer to use with epoxy primer/mastic?


There was a fair bit of seam sealer which seemed original in both shells I had, both has a type of bitumen or mastic black sealent in areas and one shell had beige stuff that had turned very brittle and chalky.


If you, or anyone is interested, here's my build thread....

http://www.boards.ie/vbulletin/showthread.php?t=2057197258

 

[steveo3002]

tiger seal is fine yes

 

[500e]

Spit 5 your at it again #9

 

[SpitfireIV]

Spit 5 your at it again #9

I've learned my lesson.

Picked up a litre of epoxy primer, tiger seal and gravitex stonechip Not gonna use the epoxy mastic; keep it simple.

How many coats of epoxy primer are recommended? I see conflicting reports between one and two....

I also picked up some U-Pol Barcoat; as I have the interior treated, rust primed and seam sealed I figured the barcoat would be worth a shot rather than the headache of stripping the whole lot back.

 

[steveo3002]

ask the place that sold it for a tech sheet , should have the mixing instructions and how many coats and how long etc , chances are 2 coats should see you right , but best to check what the maker suggests

or mention the brand here and someone might be able to advise

myself i would try the epoxy on the interior to seal it