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SO I went and got some Klean Strip Concrete and Metal Prep from Home Depot to treat the inner rocker on my 67 S Code Convert Project before I put the inner rocker back in. Says it's phosphoric acid. Smells like CLR. Used a spray bottle to hit that and the convert reinforcement pan on the drivers side. I can't believe how it takes the rust off like right before your eyes. Anyway the whole car has surface rust on it. the previous owner had it blasted and let it sit unprotected for like 10 years. A couple of questions. It says to just put the stuff on and let it dry to treat rust. Is that really the case. and Should I just spray the whole car? Heres a pic of what I purchased as well as a few pics of the car. I did spray the drivers side a bit. Should I just keep going? And do you really just let it dry and call it good?

Car when we brought it home PRETTY RUSTY


Stuff I bought



Pics of the side of the car I sprayed

 

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If you use it, you need to make 100% certain its removed and the metal is neutralized prior to priming and painting. Primers and paints do not play well with with phosphoric acid treatments. if it were mine, I'd be re-blasting the entire car followed immediately by a good epoxy primer.
 

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I would follow the advice of re blasting the entire car then epoxy prime. Yes, you let it dry.
 

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Discussion Starter #6
Thanks, Turnall, that’s way helpful. Cmefly, I may still have it blasted but I started spraying this stuff and was quite impressed. Originally was just going to use it on the inside of the outer rocker to hit the small amount of rust I couldn’t get manually. But this just seems too easy not to do it. Was thinking the phosphoric acid and then Master Series.
 

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Master Series Silver is totally compatible with phosphoric acid!
 

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Discussion Starter #14
https://forums.vintage-mustang.com/build-forum/941465-66-code-hardtop-gt-7.html#post8344817

You can see my engine bay on my 66 GT using phosphoric acid. It looks like hell just sprayed and left. Not sure how any of the paints would adhere to it that way. If you look around on my build thread that's linked, you will see I used master series silver over the acid after wiping it all clean and have had no problems.

Allen
Right on. The white stuff kinda freaked me out there for a sec. I just got done wiping down. Looks much better.
 

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Discussion Starter #15
Stop screwing around and blast the car. You are at risk of not getting all the rust treated properly.
I’ll probably do both. I have the inner rocker out on the drivers side and was using the stuff to get a couple of places I could not get to. We’ll see. I have already contacted a dustless blasting place that will blast the car for 1000.00 at the house. I want to get the floor put in it and then have him come hit it. In the mean time I’m still screwing around with this stuff. I’ve been known to overkill things. Just how I am.
 

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I keep a 5 gallon bucket filled with 4 gallons of phosphoric acid and soak my rusty parts in it until bare metal. I then rinse well with water. For surfaces on my mustang with rust that I can't easily get to, I spray with phosphoric acid, cover with a paper towel then spray some more. I then cover with some plastic to keep it from evaporating. Respray as needed then rinse well with water.

Depending upon the manufacturer, some say to spray then let dry before painting. Leaves too much residue for restoring a mustang if you ask me. Others such as por-15 metal prep say spray and let sit for 20+ minutes then rinse off with water. Let dry then paint.

I always go with option 2, spray, let sit then rinse with water before the acid has dried. The acid serves three purposes. It removes the rust, stops if from developing new rust and etches the metal so paint will grip better.

The reaction of phosphoric acid with the metal and rust and a rinse with clean water will be plenty to neutralize it.

Can you guess what's in self etching primer to make is etch? phosphoric acid.
 

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I’ll probably do both. I have the inner rocker out on the drivers side and was using the stuff to get a couple of places I could not get to. We’ll see. I have already contacted a dustless blasting place that will blast the car for 1000.00 at the house. I want to get the floor put in it and then have him come hit it. In the mean time I’m still screwing around with this stuff. I’ve been known to overkill things. Just how I am.
As long as you blast it when you are done then you will be fine. This is not a step you want to skip. Make sure to epoxy prime as soon as you can after blasting it.
 

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I use Ospho on the bottom side, inside floor and engine compartment. The trick is to treat an approximately 2 sq ft section or however big a section that you can handle, with the Ospho. Let is sit for about 10 minutes, then hose off with plenty of fresh water. Immediately after the fresh water rinse, dry it off. I used towels and then my leaf blower to insure all the water was gone. After the Ospho treatment my car stayed inside for about a year and no rust reappeared, except for a couple of spots where my sweat had dropped on it. And this is in an area that routinely sees 98% humidity. I primed the treated area with Kirker Endura Prime Epoxy


The white residue is an oxide that forms if the Ospho is not completely neutralized. It can be re treated or simply sanded off.

I also tried a bottle of PickleX 20, it's like Ospho on steroids and very expensive. A 16oz bottle of PickleX20 is about $50.00, a gallon of Ospho is about $35/gallon.
 

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Be aware the Ospho referenced isnt the same as the stuff you get at a home improvement store. And please dont use master series on the exterior of your car under the paint. Master series isn't magic, its just a moisture cured urethane. A properly media blasted car with a coating of good quality epoxy will always create a better result than half *** coating poorly prepped metal with magic potions like por15 or master series.
 

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Discussion Starter #20
Be aware the Ospho referenced isnt the same as the stuff you get at a home improvement store. And please dont use master series on the exterior of your car under the paint. Master series isn't magic, its just a moisture cured urethane. A properly media blasted car with a coating of good quality epoxy will always create a better result than half *** coating poorly prepped metal with magic potions like por15 or master series.
I wasn’t going to hit the whole car with Master Series. Just inside the rockers and some of the inner structures..I used it on the other Mustang I had on the convertible rain gutter and under structure. I was pretty impressed with it. I didn’t paint over rust. I removed all the rust and then painted the Master Series silver on the pieces. I figure if they paint bridges with it back east it will last forever where there’s no light. This car won’t be a daily driver and the only moisture it should see is when it gets washed.
 
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