Problems Stripping to Bare Metal

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PostPosted: Thu Apr 07, 2022 3:08 pm
on the 9227C i showed above I use 7" and 8" if I can find them, they require more power. 8" is much, much faster than a 5or 6" D/A. then it makes a very good buffer.
Jay D.
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PostPosted: Fri Apr 08, 2022 7:53 am
96EbonyBird wrote:
clubairth wrote: With that much to strip and no compressed air have you considered a stripping tool?


I hadn't considered that, only because I didn't want to buy a power tool that I would only use once... but I suppose doing that would be cheaper than paying someone for sandblasting.

I did try my power drill with a 5" backing pad and a 40 Grit disc and that did remove the paint faster, but it was also very hard to avoid random scratching of the metal... I guess I just need to practice more.

Thanks!

youll end up using that power tool ( angle grinder)more than once in the future.they are a useful tool.
youll have better control with it over the drill,too.

youre going to want a scratch pattern on the metal for the primer( please use epoxy primer on bare metal) to bite/grab/stick/ hold onto the metal.



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PostPosted: Fri Apr 08, 2022 9:48 am
:goodpost: after the 36 grit i use 80 grit 6" on my D/A to clean it up and prepare it for an epoxy coating.
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PostPosted: Fri Apr 15, 2022 2:38 pm
Okay, for those of you who might be interested, here's where I am with the project now (see photo below):

RoofStripped1a.jpg
Half of Roof Basically Stripped


The right side of the roof is basically stripped (not the upper right edge, because there is a moulding there which I don't want to remove until I am ready to epoxy prime, since the car is outside and that moulding seals the interior).

badsix wrote:: after the 36 grit i use 80 grit 6" on my D/A to clean it up and prepare it for an epoxy coating


Yes, that's what I ended up doing here. I used a power rotary drill with a 5" 3M stripping disc, then a 40 grit on my 6" DA and then an 80 grit on the DA. However, the finish isn't exactly perfect yet, as you can see in the following photo:

RoofStripped2a.jpg
Dark Spots


Note the faint dark spots, which I believe are some form of corrosion (rust, but not loose rust, obviously). Since the roof flexes in the middle, my DA can't get enough grip on the surface to remove those spots. I could attack them with the stripper disc on the power drill, but I'm reluctant to apply that much pressure to a focused area... am I being too cautious?

As an alternative, I've read here and on other forums that epoxy primer acts a sealer, so can it be applied directly on a surface like this, or should I keep working on removing those spots?

Thanks all!



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PostPosted: Sat Apr 30, 2022 10:16 am
Yes that's rust embedded in the metal. It's up to you but shiny is always better. As others have posted maybe go over it again with 80 grit on a sander?

I hesitate to recommend any rust remover stuff like phosphoric acid as I my opinion that creates as much or more problems than leaving the rust. Depending on your technique of course!

What level do you plan to take the car to?
Daily driver or show car or somewhere in between?
Is this for you to practice on in preparation for another project you plan in the future?

I would wipe the bare metal with clean white rags until you no longer get any black off the surface. Now apply 2 coats of your favorite Epoxy primer. I like ********** Epoxy and use nothing else but again there are a lot of products and use the ones that work best for you.
https://www.southernpolyurethanes.com/epoxy-primer

Notice I did not mention what to use as a cleaner because that again is another subject you need to decide on.
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PostPosted: Sat Apr 30, 2022 12:01 pm
clubairth wrote:Yes that's rust embedded in the metal.


Yeah, it may have been obvious to those of you who have done this before, but I'm just now understanding what is happening here. The corrosion has created pitting in the metal, and it's the pits that have rust in them.

I'm no expert, but it seems to me to be a bad idea to keep removing good metal just to get down to the rusted metal, so at this point I'm looking at other ways to deal with the rust.

clubairth wrote:I hesitate to recommend any rust remover stuff like phosphoric acid as I my opinion that creates as much or more problems than leaving the rust. Depending on your technique of course!


I've read a lot of good advice about that here... I think the key is neutralizing the acid before priming (by applying a fresh coat of acid and then immediately washing that off really well) so I'm going to try that.

clubairth wrote:What level do you plan to take the car to? Daily driver or show car or somewhere in between? Is this for you to practice on in preparation for another project you plan in the future?


The car runs well, and some body panels look okay while others have lost the clear coat or are rusted, so the goal is just to make it all look "okay". And it also is an opportunity to practice for two other cars I have that are in much better condition but need some spot touch-ups.

Thanks!



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PostPosted: Sat Apr 30, 2022 12:25 pm
It's up to you but after many long years I will tell you for a fact that if the rust is not 100% removed the odds are very high you will see it again. Rusty metal is NOT good metal. Now I will back up a bit if your using Epoxy as it does seem to be better at sealing the surface for good regardless of what's underneath.

Try the Phosphoric acid. It's a lot like soda blasting. Yes it can work well but you have an uphill battle making sure all the material is removed/neutralized before laying any paint down. I have used it in the past before I dropped back to my default position which is you gotta remove the rust no matter what.

Be sure and read your paint manufacturer recommendations as they also have different opinions on what to use.
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PostPosted: Sat Apr 30, 2022 12:37 pm
:goodpost: :goodpost: I know it doesn't get many recommendations here, but on a situation like this i like to use a good etch primer. (etch has phosphoric acid in it that will control the rust stains) i then top it with my high build primer. you can spray the etch prim letting it flash the recommended time then shoot your primer right over the etch. no sanding of the etch needed, if done in the recoat time specified usually around 24 hours. this is a proven method its is what most auto body shops do.
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PostPosted: Sat May 21, 2022 10:03 pm
I've been through every step your starting. After the strip job I used the ppg one choice conditioner system.
I chose that route for a few reasons, the first, I needed something on the bare steel so it would keep for a minute, also I didn't want to grind down to the lower lying and teeny rust.
I spoke to the local ppg region rep about the month pause between the conditioner to primer phase. Here's what I learned, if you use an acid conditioner system, be ready to paint epoxy prime soon after. He suggested I sand the surface after the long break to prep it for dtm cre primer, I did. I'm sufficiently satisfied any remaining micro and low lying rust are properly treated.
Where I live, my stripping options are limited. If I lived where you do I'd call fresh steel. I know we talked about it before, but after what I've been through I'd have definitely chosen that option with dtm cre applied the second the moisture is gone...
I just wouldn't do it the way I did it again if I had the blast option.
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