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What Pete says. EVERY manufacturer uses a bare metal prep (etch) prior to painting. This conditions the metal surface so that paint will stick as well as removes any mill scale or foreign ferrous metals. .

While all manufacturers use a specific prep product I think it should be noted that they are not all created equal. SPI uses a water born W&G remover with a specific PH. It is not a muriatic acid based converter and they explicitly state not to use acid before using their epoxy. So not EVERY manufacturer uses etch. Metal prep yes.

PPG dplf epoxy can be sprayed using regular old dx330 w&g and does not require a converter if film build is adequate but does play nice with acid converters.

Many epoxies can NOT be sprayed over an acid etch primer for example ( zinc based).

The PH of the metal can be more temperamental to different brands than others. Kirker seems to be more resilient to acid from what you guys have said on the forums. SPI is not.

I was taught to rely on the mechanical bond of the epoxy to the 180 da crosshatch to clean metal and not to rely on a chemical bond. Soda blasted cars need to be neutralized in many cases as the PH of the metal is incorrect. You guys with kirker seem to have found it works well but I wouldn't lump all epoxies in saying they will all play nice with another prep/acid product.
 

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While all manufacturers use a specific prep product I think it should be noted that they are not all created equal. SPI uses a water born W&G remover with a specific PH. It is not a muriatic acid based converter and they explicitly state not to use acid before using their epoxy. So not EVERY manufacturer uses etch. Metal prep yes.

PPG dplf epoxy can be sprayed using regular old dx330 w&g and does not require a converter if film build is adequate but does play nice with acid converters.

Many epoxies can NOT be sprayed over an acid etch primer for example ( zinc based).

The PH of the metal can be more temperamental to different brands than others. Kirker seems to be more resilient to acid from what you guys have said on the forums. SPI is not.

I was taught to rely on the mechanical bond of the epoxy to the 180 da crosshatch to clean metal and not to rely on a chemical bond. Soda blasted cars need to be neutralized in many cases as the PH of the metal is incorrect. You guys with kirker seem to have found it works well but I wouldn't lump all epoxies in saying they will all play nice with another prep/acid product.
When I said "manufacturers" I meant AUTOMOBILE manufacturers, not COATINGS manufacturers. Also, when etching ferrous metals, it IS a mechanical bond, not a chemical bond. The etching provides a significant increase in surface area for bonding. Lastly, ALWAYS refer to the tech sheet for the products being used to ensure compatibility with each other.
 

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First, don't tell me how I should think. That isn't your business. Second, you turned it into a pissing match when you downgraded my suggestions as unnecessary or incorrect way to handle rusted metal..

I'm sorry you feel that way, Pete. I thought we could discuss like men but I see (read) that you are too upset to do that.

I didn't say your suggestion was wrong or incorrect. Just that in my opinion it was unnecessary to spray an entire car with rust encapsulator. The primer I spray doesn't do well with acids and I've never had a need to do that either to that extent (entire car).

I even asked you if you could elaborate (at least for the sake of discussion and the OP) but I guess not.
 

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when i said "manufacturers" i meant automobile manufacturers, not coatings manufacturers. Also, when etching ferrous metals, it is a mechanical bond, not a chemical bond. The etching provides a significant increase in surface area for bonding. Lastly, always refer to the tech sheet for the products being used to ensure compatibility with each other.

+1

TOTALLY thought you meant coating manufacturers.

10-4
 

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I'm going with Pete here. After sanding down very thoroughly I can't see there Not being very small black spots of rust still imbedded in the metal. I know that I have them everywhere.

I agree that shooting the entire shell with MS is probably overkill,.........but that's what I'm doing.:smile2:
 

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I'll offer this. Last winter I had someone call me up to consult him on how to tackle the body work on his project. He's doing it himself but wants guidance. It's an old chev that had the bad primer from the factory. Super straight but lots of surface rust:

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I told him to sand it with 80 on a DA and call me in three days. He asks me three days later what kind of product he can use to convert the surface rust. I say send me a pic:

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At this point all he's used is a DA and he's concerned about the areas at the top of the box but he's convinced he's done sanding. I tell him at that point he's just smearing the oxidation around with your dirty disc and not getting rid of it. I say wipe it down with laquer thinner and use clean 80 grit discs and keep repeating.

He calls me a day or two later and asks is this clean enough? Are these black specks rust? (This is the top of the box from the above pic and the Lower door)

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I say yes. That is surface rust. Switch to 180 grit and keep cleaning with laquer thinner. You are not done sanding yet. He keeps repeating until his sanding discs are clean and no residue is on the wipe-all and all that's visible is clean 180 crosshatch. Zero specks visible anywhere. Then switch to W&G remover and spray two coats of epoxy after masking/blowing down/ect.

I won't bore you with every detail but i guided him with gun setup and what/how to spray, sanding processes, ect.

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This was a normal guy, do it in your garage paint job. Surgical cleanliness on bare steel with no acids or converters. He said he could have ate off the steel before he sprayed the epoxy. I told him after the epoxy he could roll it outside. It's weatherproof. The above pic is the final result of his first paint job.

In a nutshell that's the process I use and have had success with. Like it or hate it that's how I get the vehicle to the 'epoxy' stage.
 
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You do realize there is no such thing as a smooth surface. Every surface has grooves, pits, scratches, what have you. They are small and you can't see them.Ferrous Oxide lives in these areas too. I'm not saying paint ( which contains binders, "glue", in them} won't stick . . but for how long??? But I'm saying that it will stick better if there is no rust left. On an exterior piece of sheet metal, that is fairly easy to do, with a scrub of PA. So why leave it? I mean, you don't have a few more minutes to spend?
 

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I mean, you don't have a few more minutes to spend?

The epoxies I spray have never specified acid and SPI in particular specifically says not to so its just something I don't do in most cases.

Once in epoxy the metal can't oxidize anymore. There is no moisture so whatever unseen oxidation left is stopped in its tracks and can't spread. Never lost sleep at night worrying about oxidization on the microscopic level using the above process.
 

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Pete,

What prep do you do after spraying MS? What primer do you use on top of it? I have only used it once. I found it very hard to stir/mix. I tried brushing it on a floor and found it didn't brush well. It seemed to need thinning, but the packaged said it wasn't required. I am planning to spray the remainder to reach into hard to get areas. What do you thin it with to spray? What size gun nozzle do you use? What pressure? Thanks
 
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Something some of you might not realize . . . Master Series silver is a primer. It's not like using POR then topcoating. It is intended to be topcoated, it is a primer. So spraying an entire body with it isn't weird at all, it could be considered normal. There are shops that spray their bodies with it as soon as they come back from blasting. I just wanted to be clear about i as I believe some don't fully under by the comments that have been made. However I use the hell out of epoxy I don't have a problem with anyone using epoxy, I do many times and even block with it. But I do think you are missing out if you don't treat the bare rusted metal first with a chemical, then spray MS or epoxy, whatever.
 

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I'll add one other thing that most people won't realize.....
Surface rust is a painters best friend. It's living proof that the surface you are spraying has been neutralized. Surface rust is easily cleaned with a DA or a scotchbrite pad.

I just got off the phone with Kirker's rep, Kyle, and he said specifically NOT to use straight Phosphoric Acid and use a prep product instead as they only contain 10-15% PA. Im unaware of any paint manufacturer who would recommend Straight PA. Call them and see for yourself. So for anyone wanting to play garage chemist, go right ahead.

I spent a lot of time and money learning the autobody trade. I am a graduate of Wyotech's Streetrod/chassis fab/auto body/collision/high perf engines program. That may not lend any credibility to what I'm saying and I'm not saying it to toot my own horn but here's what $48,000 of tuition in 2004 taught me about converters:

Any time you put acid on a substrate it needs to be neutralized. If you don't, adhesion WILL suffer. Phosphoric acid by itself will actually self neutralize. It does this through moisture in the air. You will know when it's neutralized because surface rust will start to form. Problem is we don't know how long this process takes. Could be 3 months. Could be a year or longer.

Here's how I was taught to neutralize a car that has been exposed to Phosphoric acid: You can only neutralize with the panel wet. So rewet with your prep solution, I use Ospho (don't/can't/won't recommend straight PA, personally ). Then with the panel wet, wipe it down with a wipe soaked in water. Then Wipe dry. You can repeat this process as necessary if you don't feel you got enough conversion. Then sand with 80/180, wax&grease remover, spray epoxy. Most times I won't do this as I feel it's unnecessary unless the metal is badly pitted. The epoxy I spray has etch properties in it and doesn't need the conversion process.

Funny thing is Bart with his diluted ospho method may be doing this same thing with one less step! He's neutralizing his acid and probably didn't even realize it!

There are ways to test adhesion levels. The poor boy way is to let your epoxy cure for a month and put a golf ball shaped/sized blob of filler on the epoxy. Let it sit for 15 minutes and try to pry it off. If the epoxy/filler lifts, bad. If you can't get either to come off (golf ball will break) but layer of filler/epoxy still on, good. Try it with acid and see what happens.

The scientific way is to use an adhesion tester:

ImageUploadedByAutoGuide1464791893.267397.jpg

I would call and ask Barry of SPI what he thought of PA, but I don't need to. I already know the answer. Barry uses a professional adhesion tester and I'm sure he will gladly talk to anyone what he thinks of unneutralized acids and converters if you give him a call. I mean don't take my word for it. Call the professionals and get their opinion.

I would suggest to anyone on the fence about what method to use to CALL THE MANUFACTURER. If they don't recommend the exact method and products then don't take someone else's word for it and mixing and matching chemicals and paints on a forum. Me included.

I'm not trying to start a *****stirm, and I think Pete and I will have to agree to disagree on this certain subject. I respect the hell out of Pete and his knowledge. It's just a conflict of opinion. He has his method and reasons for doing it and I have mine. Unless someone wants to pay me back my tuition and guarantee my paint jobs for me I probably won't be changing my ways any time soon.

If you search the SPI forum for phosphoric acid you will find days of reading material and how to properly neutralize an acid before spraying to promote better adhesion characteristics. Again, don't take my word for it. Do the adhesion tests and see for yourself what happens to an unneutralized substrate.
 
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Who said to use straight Phosphoric acid? In an attempt to make me look bad, you have invented facts. You need to know more about what you are discussing. You need to know the chemical composition of phosphoric acids that are available. Then you can make an intelligent comment. Right now , it looks bad.
And as a side note, I spoke with a Kirker R&D person many years ago. We discussed the attributes of Kirker epoxy and so forth. I can't believe it was coincidence, but after having a good discussion about the epoxy, the company started advertising Kirker Epoxy as sandable. Before and when I called, they had it marked as non-sandable.
 

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Who said to use straight Phosphoric acid? .


I thought you did. 2nd post. First sentence. And unless I missed it I saw no one make any mention of neutralizing or even diluting it other than Bart. The way I read it was PA, master series, Kirker.

I'm not trying to make anyone look anything. If we could meet in person and drink a dark whiskey about it I'm sure the way both our words are perceived over the 'internets' would be much different in person. Unfortunately we love on different sides of the country though we share common interests.

I've seen too many problems with PA to recommend to someone to use PA, master series, kirker as I thought you suggested.
 

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While there are some coating pros here in the thread I'd like to interject a question. I am preparing to strip the original paint off my car. there are a lot of tiny pits on the roof and I don't think sandpaper will get them all out. I do have some naval jelly but haven't used it yet. BUT the glass is out of the car, I have a new headliner in it, and the dash has already been finished. Is it possible to treat the top without destroying the dash and or headliner? If this car was in your shop how would you attack it?
 

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I'd like to interject a question. I am preparing to strip the original paint off my car. there are a lot of tiny pits on the roof and I don't think sandpaper will get them all out. I do have some naval jelly but haven't used it yet. BUT the glass is out of the car, I have a new headliner in it, and the dash has already been finished. Is it possible to treat the top without destroying the dash and or headliner? If this car was in your shop how would you attack it?

In a perfect world I personally would use crushed glass media and reclaim the media. 80 grit/180 grit, W&G remover, SPI epoxy. Done.

Since I don't have a media booth haha, I would start stripping the paint with a strip-it disc:

ImageUploadedByAutoGuide1464812049.718826.jpg

Then switch to 80 on a DA once every bit of paint is gone. Clean/sand/clean/sand. At that point I would assess any pits. If I still had pitted material (you probably won't) then I would use the phosphoric acid based product Ospho(or similar). BUT ONLY IF IT GETS NEUTRALIZED. I wouldn't even have a problem using navel jelly or phosphoric acid, BUT ONLY IF IT GETS NEUTRALIZED. Simply wiping it off is not neutralizing.

Then 80/180. W&g remover and SPI epoxy. If I can get the metal clean enough I much prefer to not use any acid. For me it's a last resort. Not my first go to. I've seen it create way more problems than it solves when used improperly. And using it properly can have a steep learning curve. Once your paint gets in the sun for a few days.

In the SPI camp there are some that will neutralize a car to the point they are spraying epoxy over steel that has lightly flashed over. I haven't drank enough of the kool-aid to consider that but some claim it sticks like glue. Even the Kirker rep, Kyle, mentioned there's no problem spraying their product over lightly flashed metal. That's how awesome these modern epoxies are. They seal in everything and don't allow moisture to reach the surface and have binders to 'glue' to the metal. Adding unneutralized acid throws a wrench in the mix and the adhesion can be greatly diminished (40-80%).

Use 2" masking tape and 'backtape' it around the perimeter of your windshield opening. Then stretch painters plastic around it and trim the excess to avoid anything ruining your interior.

That's just my humble, naive, unprofessional way of how I would deal with the situation.
 

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Petes ponies how is it to spray? I have a gun but have only used it a few times

To answer this question, it sprays great. I don't thin it but it is thick with a lot of solids, which is a good thing. It will flow out perfectly smooth and leaves no orange peel. I use it as an aluminum paint as well for parts I want to look like aluminum or metal.


Sent from AutoGuide.com Free App
 

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In a perfect world I personally would use crushed glass media and reclaim the media. 80 grit/180 grit, W&G remover, SPI epoxy. Done.

Since I don't have a media booth haha, I would start stripping the paint with a strip-it disc:

View attachment 419817

Then switch to 80 on a DA once every bit of paint is gone. Clean/sand/clean/sand. At that point I would assess any pits. If I still had pitted material (you probably won't) then I would use the phosphoric acid based product Ospho(or similar). BUT ONLY IF IT GETS NEUTRALIZED. I wouldn't even have a problem using navel jelly or phosphoric acid, BUT ONLY IF IT GETS NEUTRALIZED. Simply wiping it off is not neutralizing.

Then 80/180. W&g remover and SPI epoxy. If I can get the metal clean enough I much prefer to not use any acid. For me it's a last resort. Not my first go to. I've seen it create way more problems than it solves when used improperly. And using it properly can have a steep learning curve. Once your paint gets in the sun for a few days.

In the SPI camp there are some that will neutralize a car to the point they are spraying epoxy over steel that has lightly flashed over. I haven't drank enough of the kool-aid to consider that but some claim it sticks like glue. Even the Kirker rep, Kyle, mentioned there's no problem spraying their product over lightly flashed metal. That's how awesome these modern epoxies are. They seal in everything and don't allow moisture to reach the surface and have binders to 'glue' to the metal. Adding unneutralized acid throws a wrench in the mix and the adhesion can be greatly diminished (40-80%).

Use 2" masking tape and 'backtape' it around the perimeter of your windshield opening. Then stretch painters plastic around it and trim the excess to avoid anything ruining your interior.

That's just my humble, naive, unprofessional way of how I would deal with the situation.
Thanks Riley, trying to get it done without messing up the inside. I have heard good things about SPI from Rusty and now Pete has me interested in Master Series as well
 
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Here's some recent pics . . .

First pic shows the trunk lid sprayed with Master Series silver. If the lid was good with no problems, I wouldn't have sprayed MS. But it had some pics and surface rust. So the lid was treated with phosphoric acid, then Master Series, then epoxy primer. The pic just shows the Master Series.
The next pic is a floor section. I always paint the floors with MS.
The third pic is a welded seam when installing a quarter skin. I also paint as welds, front and back best I cam, with MS. If epoxy was used for this, probably fine as well. But you want something down in the nooks and crannies of the weld. Then I scuff it up and apply filler on top of the MS. That way there will be no moisture ever getting to the skim if filler, no bubbling.
 

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