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Old 03-23-2017, 08:32 PM
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Sandblast, Ospho, Vinegar

Summer is coming shortly and hoping to get the coupe in epoxy. Before priming I would like to tell the processes I went through and the results, well the results explained to me.


Coupe had very heavy surface rust with no traces of any paint or primer. Started by sandblasting with blasting sand. After the blasting, I still had very small specks of rust deep in the rust pits. Figured these pits were smaller than the sand grains which couldn't reach the bottom of the smaller pits. The same day I brushed/rubbed ospho over the entire coupe removing the very small rust specks in the smaller pits. The metal looked very good with a slight grey color. Was impressed with the ospho results. Left the coupe outside overnight and a very slight surface rust reappeared where the overnight dew had settled. I then reapplied the ospho and easily removed the new surface rust. Never rinsed ospho with water, just wiped off the excess. Then parked coupe in an enclosed garage. Couldn't leave things alone so I applied vinegar to the roof section to see what would happen. Had watched "My Friend Pete" on youtube apply vinegar to treat surface rust. After returning the coupe looked just like the car Pete had treated with vinegar. Very heavy rust coating in the vinegar coating. This is where I am confused on what happened. I knew from the video this would happen when applied over surface rust but I had removed all rust by blasting and applying ospho. Where did this rust come from. When I wiped the vinegar/rust from the surface it had turned all the metal surface black. I then applied another application of osho to remove the black coating from the metal but it required scrubbing very hard to remove. Can someone explain what happened here with the vinegar and rust appearing. This was two summers ago and I plan on reapplying the ospho to wet then rinse very well with water. After drying will apply a couple coats of SPI epoxy primer. I'm wondering about what will happen between rinsing and epoxy in reguards to flash rust. Any thoughts or suggestions would be great.


Have a great day,
Bob

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Old 03-24-2017, 06:34 AM
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No Idea, what was the vinegar supposed to do?
Ospho wont remove rust if you just brush it on it will just convert it and give you problems as soon as its primed. If your lucky the problems will start before you put a couple hundred hours into it.
Heres how its done.
Removing heavy surface rust with Ospho.
1. sand rusty surface with 80 on a da sander to get the loose stuff off.
2. doing one panel at time, apply 12"x12" nice and wet let it sit for a minute and scrub it in with a red scuff pad,wipe off dirty ,nasty access as much as you can using paper shop towels (not from your kitchen) the blue ones work too.
3. keep doing this until the whole panel is done then do the whole panel at one time keeping the whole panel wet. wipe of access and apply another wet coat wipe it dry. let it sit 24 hrs sand it with 80 again then repete the process until you don't get any rust color coming up. If theres pits go right over them, leave them for later they'll get special attention.
This is only how to remove heavy surface rust and keep the panel from rusting again even outside it wont rust for a long time.
Theres a coating that needs to come off before you prime and theres another procedure for doing that.
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Old 03-24-2017, 06:37 AM
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surface rust

u have a chemical reaction with the vinegar. and then let it set toooo long without any protection. hence= bare metal. there are others here that can provide better info to get the surface rust off, but then u need to wipe with paint prep and paint it with at least primer. even in a garage with bare metal it'll rust..
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Old 03-25-2017, 07:09 AM
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Quote:
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No Idea, what was the vinegar supposed to do?
Ospho wont remove rust if you just brush it on it will just convert it and give you problems as soon as its primed. If your lucky the problems will start before you put a couple hundred hours into it.
Heres how its done.
Removing heavy surface rust with Ospho.
1. sand rusty surface with 80 on a da sander to get the loose stuff off.
2. doing one panel at time, apply 12"x12" nice and wet let it sit for a minute and scrub it in with a red scuff pad,wipe off dirty ,nasty access as much as you can using paper shop towels (not from your kitchen) the blue ones work too.
3. keep doing this until the whole panel is done then do the whole panel at one time keeping the whole panel wet. wipe of access and apply another wet coat wipe it dry. let it sit 24 hrs sand it with 80 again then repete the process until you don't get any rust color coming up. If theres pits go right over them, leave them for later they'll get special attention.
This is only how to remove heavy surface rust and keep the panel from rusting again even outside it wont rust for a long time.
Theres a coating that needs to come off before you prime and theres another procedure for doing that.
After the fist application dries, using a wire wheel or wire cup works well on removing the stubborn surface rust, just wheel while wet you'll see the difference right away, just don't let it start drying and always wipe off as much as you can because the more ospho you leave on the more that has to come off when you prime. Spraying it on and walking away wont get good results.
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Old 03-25-2017, 08:18 AM
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All the rust except in the bottom of the small pits were removed during the sandblasting stage. Used the ospho to treat and remove the little specks of rust in the bottom of the pits. There wasn't much or very many specks. Thought I read here that was the process after blasting.


How do I treat the pits? Was planning on wetting again with ospho and sanding with pad, then rinsing with water to remove and neutralize. Then after drying prime with epoxy. Is this correct or is there more?


I didn't understand the rust in the vinegar. Where did this rust come from.There wasn't a little bit it was solid rust in the vinegar coating. I've never used vinegar before so I wasn't sure what the results should have been. After watching the "My Friend Pete" youtube video, I expected rust to be in the vinegar coating if applied over surface rust, but didn't expect to see rust when applied over rust free blasted and ospho metal.
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Old 03-25-2017, 02:07 PM
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Any chemical consisting of acid will initially eat away at rust however the residual acid left on the metal surface will start to induce rust in an accelerated manner. Most household vinegar consists of 3% Acetic acid hence the source of oxidizing agent which resulted in your rusted panel. Ospho (product name) is Phosphoric acid which has the ability to turn iron oxide (rust) into iron phosphate state. This leaves a rust incapsulated with a dull black coating which is chemically stable unless it comes in repeated contact with air and water. If there's possibly any way that anyone can seal out moisture and air out of this surface, then the rust under the phosphate coating will become inactive. Since keeping the moisture out is questionable, most people in the know will choose to use the Ospho to dissolve the rust rather than for its intended use. As someone suggested earlier, use a wire wheel in conjunction with Ospho to dissolve the rust in the pitted areas.
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Old 03-26-2017, 09:05 AM
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Quote:
Originally Posted by highvolt View Post
All the rust except in the bottom of the small pits were removed during the sandblasting stage. Used the ospho to treat and remove the little specks of rust in the bottom of the pits. There wasn't much or very many specks. Thought I read here that was the process after blasting.


How do I treat the pits? Was planning on wetting again with ospho and sanding with pad, then rinsing with water to remove and neutralize. Then after drying prime with epoxy. Is this correct or is there more?


I didn't understand the rust in the vinegar. Where did this rust come from.There wasn't a little bit it was solid rust in the vinegar coating. I've never used vinegar before so I wasn't sure what the results should have been. After watching the "My Friend Pete" youtube video, I expected rust to be in the vinegar coating if applied over surface rust, but didn't expect to see rust when applied over rust free blasted and ospho metal.
Why worry about the vinegars reaction You shouldn't be using it at all.
Pitts need a stiff wire wheel and Ospho and sanding pad will only get the surface and wont get down in the pitts. You can also try mixing a bit of blasting media in with the Ospho ,This will get down in there too. A da with a scuff pad stuck on the pad or a rol-loc fiber wheel (gasket cleaner) will get that sand slurry down in there and give it a good scrubbing too. Then wipe it all off as much as you can and let it dry. After its dry wire wheel it again rewet it with Ospho and rinse it off with water, using shop towels and air, blow it dry asap. Any flash rust caused by the water can be removed with the wire wheel just before priming. Always, always, always, use a good quality wax & grease remover to clean your metal before you prime and clean it at least twice. Always test for adhesion after primer has cured before moving to the filler stage of the job.

Last edited by deadbodyman; 03-26-2017 at 09:14 AM.
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Old 03-26-2017, 11:56 PM
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Oh, I don't plan on using vinegar again. Was just confused as to where the rust came from. Rust was 99% removed by the blasting and 1% removed by the ospho.
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Old 03-27-2017, 07:08 AM
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Everything sounds good so far just be carefull, maybe prep one panel and prime at a time. You can even dilute the ospho about 50% for your final prep, it'll still get off the older stuff and wiping it all off with a damp towel a few times should get you there. Use lots of damp towels
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