Need help with tiny rust spots

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PostPosted: Mon May 06, 2019 7:31 pm
So I’ve got days of rain coming after tomorrow and a large section of my car down to metal. This is the roof of the car where the clear had failed and there was a large round rust spot. I’ve went over the whole thing with 40 grit and tried a flap disc(didn’t want to stay on the metal long with this). What can I do here? I have ospho on hand but I’m nervous with chemicals.

Need help
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PostPosted: Tue May 07, 2019 2:28 am
Can you keep car inside during bad weather? Hope so.

That metal looks pitted either blast it clean or use a Good metal treatment. Ospho will work when used correctly, I have used it in the past. I like another product more made by Dupont currently mfg by Axalta now 5717S followed by 5718S. both products must be used together.
https://www.axalta.com/content/dam/NA/H ... 7S-Eng.pdf
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
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PostPosted: Tue May 07, 2019 4:24 am
The car is inside but shops not fully insulated yet so I worry about moisture. I planned on habit it primed before the rain came

I’ve seen mixed stuff on ospho but I used it on a rusty k member then primed/painted with no issue but that was just a k member. Any tips on the correct process? Follow the directions on the bottle or different? When I did the k member I tried to make sure the product was removed from the surface before primer. I believe the bottle says to just leave it.

I will look into those products. Thanks

Edit::: all I have local is a Parts store that carries ppg products. Is there an equivalent to your suggestion?

Also I do have a spot blaster I was hoping to avoid using but I’m starting to think I need to just try to weather the storm and attempt to keep as much flash rust off as I can for the moment then once the rain is gone hit the roof with the blaster. I’m still very interested in the proper use of ospho and like products though. When I googled the DuPont product it actually showed ospho at the top of the page so I assume they’re similar

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PostPosted: Tue May 07, 2019 8:25 am
Removing the rust is always the best method. You have easy access to this area and a spot blaster would take care of these spots quite quickly. Spray some W&G remover on it and wipe off with clean towel. Let it flash and then shoot your two coats of epoxy primer.

I only use Ospho for areas that I cannot media blast.
Ospho works well but it might take two or three applications to get the rust completely converted. Then you need to apply another coat and immediately wash it off with soapy water to neutralize the acid. Rinse well and let it thoroughly dry.
1968 Coronet R/T


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PostPosted: Tue May 07, 2019 8:36 am
Thanks that’s pretty much what I did when I used ospho on the k member followed by epoxy and black tractor paint. It’s been over a year and it still looks great.

I’ve decided I’m gonna wait and blast the area. Right now they’re forecasting 5 days of rain/storms starting tomorrow so it will have to sit in the shop til it’s over.



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PostPosted: Tue May 07, 2019 9:55 am
Billgluckman wrote:The car is inside but shops not fully insulated yet so I worry about moisture. I planned on habit it primed before the rain came

I’ve seen mixed stuff on ospho but I used it on a rusty k member then primed/painted with no issue but that was just a k member. Any tips on the correct process? Follow the directions on the bottle or different? When I did the k member I tried to make sure the product was removed from the surface before primer. I believe the bottle says to just leave it.

I will look into those products. Thanks

Edit::: all I have local is a Parts store that carries ppg products. Is there an equivalent to your suggestion?

Also I do have a spot blaster I was hoping to avoid using but I’m starting to think I need to just try to weather the storm and attempt to keep as much flash rust off as I can for the moment then once the rain is gone hit the roof with the blaster. I’m still very interested in the proper use of ospho and like products though. When I googled the DuPont product it actually showed ospho at the top of the page so I assume they’re similar



Ospho
Let it etch in good keep it wet wash with soap and water don't be surprised if it flash rusts simply sand off residue, Pits should turn Dark black and stay dark black even after drying.
DO NOT PAINT OVER DRIED ON OSPHO! unless your using Acid etch primer and then why would you use the Ospho? That may be an avenue you wish to explore using an Acid etch Primer though?

5717S & 5718S
Alternatives? No Maybe Ospho ? But in reality it really has none
The 2 Dupont Product products work together as a Cold Galvanizing system, Its the only one on the market that I know of.
It removes and treats minor surface rust and prevents rust in future. Both Ospho and the Dupont product use Phosphoric acid but in reality that's where the comparison ends. Ospho uses Sodium Dichromate while Dupont has some other stuff in it Like NICKLE and zinc phosphate it actually deposits on the metal, It its not good for you so where gloves and a respirator if you use it.

The Dupont Product is a Cold Galvanizing system its very effective on minor surface rust and minor pitting problems its very effective at cleaning the metal for painting and prepping for paint Its the Only Acid product I have ever seen that was recommended by a Paint Manufacturer to be used on metal under there paint system!

Once the metal is treated it wont rust! I have treated many whole cars with the stuff for added rust protection and left them like that for many months with no flash rust. but I live in Mojave desert Death Valley area.
application instructions and Precautions must be adhered too this stuff is not a Toy.
Its only a surface treatment so if you sand on it Or scratch it the protection that is deposited by application is gone so once treated don't Sand it just wash with Soap and water tack it off once fully dried and Paint with a good Epoxy or Acid etch Primer.

Spot Blaster
I had one but it didn't work for me, I use a Pressure pot Blaster and Crushed Glass its very effective on Pitted metal and rusted parts, also effective for cleaning metal and removing old coatings. I have modified my pressure pot with a Air regulator to control the pressure I blast at. I use Low pressure and Keep moving don't concentrate on one area metal can and will be destroyed by staying in one spot to long in a matter of seconds no matter what pressure is used. Its a Fine line between that's good and OH $
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Tue May 07, 2019 11:30 am
The DuPont product sounds nice and I’ll definitely remember it.

My spot blaster didn’t work well out of the box. It’s a siphone style. The trick I did was to cut off the siphone tube and turn the gun upside down so it’s now gravity fed



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PostPosted: Wed May 08, 2019 11:47 am
Blasting is best as long as its all removed before paint you should be good.
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Thu May 09, 2019 5:01 pm
Yep blasting it is. Thanks guys. The weather forecast has changed I should have sun on Sunday so I can get it done.

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