# Engine bay respray disaster



## aronw2004 (Sep 19, 2013)

Hi everyone, I really need some advice. 

Iv been sorting out the engine bay on my 1986 205 gti.
I have sanded some areas, 80% back to bare metal to sort the rust out and I have sanded the rest to give the primer a good key.

Next I have primed the area with some zink phosphate I had lying around. I had to thin it @ about 10% to go through the sprayer.

I have then sprayed it with etch primer from an aerosol tin.

The cover was good but in a few areas, about 5 in total it has reacted like a blister.

Having red up online there are mixt advice on what can be put on top of zink phosphate.

I have now sanded back these areas and sprayed them with etch primer.

I plan to give it another coat before 2k filler primer and then 2k top coat.

Will I get anymore reactions down this road?

Really gutted at this moment due to the hard work iv put in, I should never of put the zink phos on in the first place. :wall:


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## steveo3002 (Jan 30, 2006)

why etch on top of zinc primer 

its only any use on bare metal ...and only one coat needed

id suggest you roar it all off and 1x etch coat , then 2k primer , should be spot on then


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## aronw2004 (Sep 19, 2013)

Its not going to be easy to take it all off, unless I get it sand blasted, witch I cant due to it being in bits at the moment. 

In hindsight I wouldn't of done it this way, but what's done is done.

What to do next is the problem, and will the rest of the paint react as well.?


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## steveo3002 (Jan 30, 2006)

no one can say for sure

either suck it and see ....or start over and do it right


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## Andyb0127 (Jan 16, 2011)

Zinc primer us mostly used as a primer for welding.
Etch primer is for baremetal as an adhesion promoter for primer.

Reason its all reacted is because you've used two different types of primer that are basically fighting against each other.

Best course of action now would be to remove all of the primers you have applied, back to batemetal. Clean and degrease thouroughly. Then apply a light coat of acid etch primer. Then I would apply an epoxy primer over all of it, reason for using epoxy is its sealer and will completley from moisture/oxygen which us what penertrates into metal causing rust an epoxy primer will.seal it of from this.


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## aronw2004 (Sep 19, 2013)

thanks everyone for the advice. 
What would you use then, if you had some areas of bare metal and some patches of sanded paint then?

Do you think the 2k filler / primer would have gone on top of the zink phos alright without the etch.

I thought the 2k primer needed the etch on first, that's why I put it on top of the zink phos.

using that zink has been a huge mistake.

I have always found it good on my machinery, i.e ride on mower and diggers, so I thought, this will stop any rust coming through. Big Mistake!!!

Some one told me that it had good adhesion properties and also quite good heat resistance. This person had used it as a primer on his brake callipers and drums.


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## steveo3002 (Jan 30, 2006)

mist some etch over the bare areas , it doesnt matter if you get some overspray on the sanded paint areas but it wont do any good on top of paint


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## aronw2004 (Sep 19, 2013)

thanks steveo3002. 
very helpful. I think the reaction migh be on the areas that had some of the original paint still on there. Ill investigate further tonight.

Thanks ever so much for the advice.


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## steveo3002 (Jan 30, 2006)

roar as much as you can off , then mist the new on very carefully , heavy wet coats are likley to upset it


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## craigeh123 (Dec 26, 2011)

Could you bar coat it and respray ?


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## Aaran (Sep 18, 2007)

etch is for etching into metal and alloys only.

most epoxy paints WILL adhere right to sanded bare steel no problems (its far better than etch in my eyes in every way, bar the cost). alot of paint branded ones will also allow you to overcoat right over an epoxy with high build primer or a basecoat in a 72 hour window (no sanding needed) i think the letchler is like this


money on the acid in the etch reacting with the zinc primer causing the issue. had it before. decent zinc primers will adhere to bare metal pretty well and you can paint right over them with high build if its rough or sanded.

zinc paints are for rust proofing/ cold galvanizing (rustbuster to a epoxy zinc primer but its mega money) and designed for seriously high duty stuff (oil rigs etc)

weld through primers are formulated for being able to weld over and not contaminate the weld, i have tried welding normal zinc primer before and its no different from welding galv steel or any other primer (it splatters and the weld is dirty and crap penetration) its main use if for rust proofing bare metal (ie a body seam thats going to be spot welded) before its spot or plug welded because once its welded you will struggle to get paint in the seam if its nice and tight

hope this helps. you could test spray some epoxy primer right over the stuff you have just painted as in most cases its very adhesive and acts as a very good sealer.


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## XRDAN (Feb 28, 2012)

high build (filler) primer will be fine on small areas of bare metal, a light coat of etch can be used but is only essential for large areas of bare metal. I would flat it down and use barcoat (paint isolator) over the whole bay, then go with high build followed by your top coat:thumb: stripping it back is an option but a lot of work and if you have good adhesion I would not bother...


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