Ospho advice.

[Evan Dutch]

Hey. I'm preparing to replace the rear floor pans in my 72 dart. I've taken the area under the pans down to bare metal as best I could. But there is some pitted rust that I cannot remove with my tools. The shermin Williams close by sells ospho. My concern: after the ospho has done its thing I plan to spray over it with weld thru primer. Then weld the panel in. Is it safe to weld over the ospho prepared metal? The sds on the product says it's not flammable but will it smoke? Has anyone used this stuff? What else can I use to solve this problem?

 

[Pete in NH]

HI,

Ospho is basically a phosphoric acid solution. It converts iron oxide (rust) into iron phosphate which is more chemically stable that rust. The bigger concern with phosphoric acid compounds is that not all primers are compatible with it and you need to be sure it is properly neutralized and removed. I think if you flush the ospho with plenty of clean water and not let it dry on the metal surface you will be okay with the weld through primer. I don't think you will have any issues with welding the treated metal although usually you would weld first then treat the metal with the acid.

 

[Mopar-Man]

Just my experience, but Ospho is an amazing product. We Ospho'd my entire car 20 years ago and then primed over it - no adhesion problems ever showed. We used PPG products. 2nd paint job was Sikkens.

 

[Howard1784]

POR 15. Hands down.

 

[Evan Dutch]

Just my experience, but Ospho is an amazing product. We Ospho'd my entire car 20 years ago and then primed over it - no adhesion problems ever showed. We used PPG products. 2nd paint job was Sikkens.

If you had any pitted rust. Did the ospho take care of it?

 

[Evan Dutch]

POR 15. Hands down.

I've heard good things about it but the price and availability is not the greatest.

 

[plumkrazee70]

If you had any pitted rust. Did the ospho take care of it?

All that Ospho is gonna do on the pitted rust is stop the chemical reaction to help stop it from continuing to rust. The pits will still be there.

I know for a fact this stuff is not flammable, because I used it on a section of my floor and then verified it wasn't flammable before welding in some bucket seat plates. Just double check with the mfg of your primer to make sure it isn't going to have an adhesion problem.

Michael

 

[Evan Dutch]

All that Ospho is gonna do on the pitted rust is stop the chemical reaction to help stop it from continuing to rust. The pits will still be there.

I know for a fact this stuff is not flammable, because I used it on a section of my floor and then verified it wasn't flammable before welding in some bucket seat plates. Just double check with the mfg of your primer to make sure it isn't going to have an adhesion problem.

Michael

Good to know. Thanks!

 

[Woods74]

Those pits are nothing to be worried about; weld it, paint it, move on.

 

[Mopar-Man]

If you had any pitted rust. Did the ospho take care of it?

Pitted? Well, it cannot penetrate very deeply. Mostly good for surface rust or as a metal etch/primer. I coated a bare piece of metal 10 years ago and it is still shiny. The other piece I didn't coat is covered in rust. It is really amazing how well it can protect. I paint over it all the time and have never had a problem. I wiped the entire inside of my car down with it after I gutted it. Now if the metal is rusted on the backside and the Ospho can't reach it, it WILL rust through. But if you can get to both side you are golden.

 

[Evan Dutch]

Pitted? Well, it cannot penetrate very deeply. Mostly good for surface rust or as a metal etch/primer. I coated a bare piece of metal 10 years ago and it is still shiny. The other piece I didn't coat is covered in rust. It is really amazing how well it can protect. I paint over it all the time and have never had a problem. I wiped the entire inside of my car down with it after I gutted it. Now if the metal is rusted on the backside and the Ospho can't reach it, it WILL rust through. But if you can get to both side you are golden.

That's cool. I'll have to try it on the roof of my dart and see how it does.