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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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 Posted: Mon May 04, 2015 12:23 pm Post subject: |
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| edredas wrote: | | jason c wrote: | 1) any primer will need a tooth to bite onto the surface, so you'll have to sand it.
2)sanding it will take the galvanizing off.
3)you will not find a primer that adheres well to the galvanizing |
Self-etching primers do exactly that.... self-etch. The factory primer adhered to the galvanized coating it quite well because it was not Alkyd based. I've been painting over galvanized steel for decades and not once have I seen the primer pop loose. Its not about experience, it's about knowing the chemistry of the paints. |
Etch primers are acid based, that's how they self etch. That acid will attack the galvanizing. Epoxies have better adhesion & corrosion resistance than etch primers and most etch primers aren't recommended for use with fillers. So what's the real advantage?
What primer are you recommending that will self etch & not remove the galvanizing? |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Mon May 04, 2015 1:31 pm Post subject: |
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| edredas wrote: | | So, you're telling me the factory galvanized the car and then sanded the galvanizing off so the primer would stick.... or maybe they used a self-etching primer? |
A self etch would attack the galvanizing they just applied. The factory has process that are impossible to replicate. |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Mon May 04, 2015 2:24 pm Post subject: |
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Opps, sorry I deleted that post... that said, the factory and all other manufacturers use a very strong self-etching primer they use on their galvanized panels, and they do not destroy the galvanizing. The self-etching primers you get at walmart aren't even strong enough to adhere, much less destroy the galvanizing.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Mon May 04, 2015 2:35 pm Post subject: |
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| edredas wrote: | | Opps, sorry I deleted that post... that said, the factory and all other manufacturers use a very strong self-etching primer they use on their galvanized panels, and they do not destroy the galvanizing. The self-etching primers you get at walmart aren't even strong enough to adhere, much less destroy the galvanizing. |
The factory's don't use a "self etch" type of primer that can be purchased, they use an e-coating process. E- coating is an electrical process, not an acid based one.
That is the black primer that you see.
Any self etch you can buy at "Walmart" isn't going to be sutible for automotive use, I don't care what the can says. Coatings in a can don't contain a catalyst, they are a 1part coating that will rain solvent sensitive. You should never apply a catalyzed coating over a non catalyzed one, it will delaminate.
The stuff at "Walmart" may be fine for you lawn mower, for your car, not so much. |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Mon May 04, 2015 7:09 pm Post subject: |
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It is not clear to me whether an E-coating was used in the Neckarsulm factory or not. I've got some pictures of them painting the cars, but nothing of the steps before that. Either way, I'll take your word for it.
That said, an e-coating is not required for paint or primer to stick to galvanized steel...
From this PDF:
http://www.galvanizeit.org/images/uploads/articles/paintprep.pdf
| Quote: | PREPARING GALVANIZED SURFACES FOR PAINTING
Successfully painting or powder-coating hot-dip galvanized steel does not have to be difficult or confusing. Just like painting or powder coating over anything else, proper surface preparation is crucial to ensuring effective adhesion. |
| Quote: | | Many types of paint and paint systems have been used quite successfully with galvanized steel. With the exception of some alkyd formulations, a variety of paint formulations have been effectively used for painting galvanized steel. |
It is highly unlikely that anyone will come across any alkyd automotive primers since every car for about the last 20 years has been galvanized. This means any primer meant for automotive use will likely work, so long as it is compatible with the type of paint you are using.
Below is a list of some primers that are approved for painting a galvanized surface. Not only are there some epoxy primers but also, a few acidic wash primers, which is the type of etching-primer I was referring to.
Jason C Said:
1. "you will not find a primer that adheres well to the galvanizing"
2. "an epoxy primer will not work on the galvanizing either."
3. "A self etch would attack the galvanizing they just applied."
I'm not sure what else I can say at this point without going in circles.
I hope this helps! 
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Mon May 04, 2015 8:11 pm Post subject: |
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| edredas wrote: | | Quote: | PREPARING GALVANIZED SURFACES FOR PAINTING
Successfully painting or powder-coating hot-dip galvanized steel does not have to be difficult or confusing. Just like painting or powder coating over anything else, proper surface preparation is crucial to ensuring effective adhesion. |
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What exactly is the "proper preparation" method?
The website you got your information from makes no reference to automotive galvanizing, its referring to industrial methods. If you had read what the preparation methods were and relate them to what the tech sheets for automotive primers (especially glasurit epoxies) say, you would (or should) realize that what your suggesting isn't realistic. That is where experience comes in, trying different methods, seeing what works & what doesn't based on trial and error.
The website you quoted:
http://www.galvanizeit.org/specification-and-inspection/specifying-duplex-systems/preparing-hdg-for-paint
Its pretty obvious that you don't really understand what you research. Have you ever attempted to prime a galvanized or bare metal 924 or any other car for that matter?
What types of galvanized objects have you been painting for "decades"?
The galvanizing on cars is so thin that even a scuff pad will remove it. |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Tue May 05, 2015 7:39 am Post subject: |
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| Quote: | | Its pretty obvious that you don't really understand what you research. |
Yawn, I didn't have to research any of that, just something that I found to help you understand. Prep is pretty much the same and in fact a electroplated cars are specifically intended to be painted...
You should probably write these scientists, chemists, engineers, and body shop technicians and let them all know that you know better!
Thanks!
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Tue May 05, 2015 7:58 am Post subject: |
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I don't need help, I've been doing this long enough. Thanks anyway.
Its quite amusing that you refuse to answer any questions about what to use or what you've done yet you continue to insist you know what youre talking about.
I guess someday if or when you try it you'll find out why saving the factory galv doesn't work for yourself. |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Tue May 05, 2015 8:45 am Post subject: |
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I'm not avoiding the question at all, just don't seem to see the point in sitting here arguing. I've painted about 20 cars in my life, not including the ones I helped with in autobody class back in 1993. While I am trained in engine building and auto body repair, that is not my profession, despite building a few cars a year for clients.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Tue May 05, 2015 9:25 am Post subject: |
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I'd prefer it be a discussion than an argument. If you've actually done what youre recommending, why not state what you used & what you used it on? I don't know why you picked the website you picked for reference but its not quite relative to the Porsche galvanizing. The galv in their references are significantly thicker than the 924 (1-2mils).
I've tried it before, you'll sand it off trying to make a proper surface for an epoxy to stick well. An acid etch will eat it, they don't work as well as epoxies and are difficult to use with fillers (no doubt there will be a need for some). Why risk an adhesion failure?
I have had adhesion failures causing me to have to strip everything back off & start over, I would like to save someone else from having problems.
If you want to do it your way, that's your right. You shouldn't convince someone to do something you haven't tried. Just because a tech sheet lists something, that doesn't necessarily make it OK in every situation. Obviously even the factory had issue with it, his car is peeling. |
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pcelenta
Joined: 16 Feb 2007
Posts: 546
Location: long island,ny
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| Posted: Tue May 05, 2015 11:17 am Post subject: |
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edredas????!??????
The primer is usually specific to the project. If you are using a single stage enamel catalyst, you must use a Sealer or the paint will not shine. Also a Lacquer primer will craze and chip with enamel over it. Urethane paint you can get away with pretty much anything as long as the primer isn't lacquer or alkyd. So, I guess the thing I'm saying is, ask the person you are buying paint from to recomend the correct primer for your project. ?????????
You must use a sealer with catalyzide enamel or the paint won't shine? Please advise which manufacturer states this.
Lacquer primer will craze and chip with enamel over it? Really? Tell that to earl schibe.
Urethane can't go over a lacquer primer surfacer? well that depends on the manufacturer. Glasurite you would have a problem. But most of the domestic urethanes can.
I am going to take your last piece of advice and say you should check with the paint manufacturer and not the person selling it to you. |
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edredas
Joined: 09 Dec 2004
Posts: 861
Location: Charlotte, NC
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| Posted: Tue May 05, 2015 3:15 pm Post subject: |
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| jason c wrote: | | Just because a tech sheet lists something, that doesn't necessarily make it OK in every situation. Obviously even the factory had issue with it, his car is peeling. |
I agree, but I have never even heard of anyone having issues before, and just wanted to point that out. I can't speculate to what is happening with his paint, but there are a number of things that could cause this and perhaps without actually seeing it there is no way of knowing. Either way I wish him the best of luck.
| pcelenta wrote: | | You must use a sealer with catalyzide enamel or the paint won't shine?Please advise which manufacturer states this. |
Look, I don't mean to be rude, but you're trolling, right?
| pcelenta wrote: | | Lacquer primer will craze and chip with enamel over it? Really? Tell that to earl schibe. |
I had to fix an issue like this once, and I was certain that the guy had used a lacquer primer, but I could be wrong. Either way, nasty things can happen when you mix systems.
| pcelenta wrote: | | Urethane can't go over a lacquer primer surfacer? well that depends on the manufacturer. Glasurite you would have a problem. But most of the domestic urethanes can. |
Again, I am pretty sure you are trolling? Urethane will eat Lacquer.
My advice was specifically for him to ask the person (usually a trained technician) what primer to use with the paint he has chosen to avoid these issues.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver |
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pcelenta
Joined: 16 Feb 2007
Posts: 546
Location: long island,ny
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| Posted: Wed May 06, 2015 12:31 am Post subject: |
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| With all due respect I am not trolling. Just pointing out that in my 30 plus years in and around automotive restoration and refinishing the statements made were less than accurate and it seems other here feel similarly. |
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jason c
Joined: 13 Jan 2014
Posts: 1018
Location: Nwi
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| Posted: Wed May 06, 2015 12:36 am Post subject: |
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| edredas wrote: | | I have never even heard of anyone having issues before, and just wanted to point that out. |
If that was the case, you should have said so instead of insisting it could be done with no specific proof or citing how you make it work. Why not ask a question as to how I prepped it & what I used?
| edredas wrote: | | My advice was specifically for him to ask the person (usually a trained technician) what primer to use with the paint he has chosen to avoid these issues. |
This is good advice on its face but you would be surprised at how much wrong information you'll get. I've got blatently wrong information from the glasurit tech line and body shop supplies. I knew it wasnt right so i talked to someone else at the same place & got the right anwser. You have to figure out who you can trust because if it goes wrong, you are the one who has to redo it. If you don't have enough experience to know that something doesn't sound right, you can get burned.
If you take it to a shop & have it done, they're going to do what they feel is right and if it peels off, hopefully you got a warantee..... |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Wed May 06, 2015 1:00 am Post subject: |
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This thread has thoroughly disabused me of the notion of attempting my own repaint.
For my next project, I'm just going to wrap it.
_________________
erstwhile owner of just about every 924 variant ever made |
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