OSPHO: Any downside to applying under truck

[67RT]

So my new Bronco has surface rust on the frame and underside. Any downside to applying Ospho? I would not cover with a primer or paint at this time. Just to prevent further oxidation..Truck is stored outside in elements but will not be driven in snow or rain.

 

[bmc69]

I've been an Ospho fan for ...probably 40 years? The only downside I've ever seen with using a conversion coating like that is if you convert scale rust...creating a passive "top coat" that protects rust underneath.

 

[67RT]

So I plan on Wire Brushing most of it off. Will the rust hidden underneath continue to progress? IS there still a source for oxidation or will it be pretty much encapsulated? I should be able to brush most of it off..

 

[bmc69]

So I plan on Wire Brushing most of it off. Will the rust hidden underneath continue to progress? IS there still a source for oxidation or will it be pretty much encapsulated? I should be able to brush most of it off..

It's a chemical conversion process..it only goes a few mil deep. So if you have scaly rust ..it won't convert that all the way through. Rust never sleeps..anything that is encapsulated will eventually pop whatever is above it off.

 

[00gyrhed]

I dont know about Ospho the produt name but since its liquid and green I assume it just phosphoric acid. You can actually wash the rust off down to bare metal with phosphoric acid. You do not have to wire brush it, but it will be faster to wire brush it where there is heavy scale but you can actually just keep brushing it into pits and the phosphoric acid will remove the rust not just convert it. If you just brush it on and leave it it will convert it. But continual application will disolve the converted rust until you get to bare metal and then it will leave a nice grey coating on the metal you can prime over after washing.


I used to work in a phosporic acid plant, it is real cool stuff. I stopped drinking cokes and dr.peppers for a long time after that though. Coca-cola and dr pepper accounted for about 10% of our acid sales and phosphoric acid is in just about every soft drink you can buy. Of course we had to filter the arsenic out of it before we coule sell it to them........ After I saw that operation I quit drinking soft drinks for several years.

We had hot rodders that worked there that would bring old rusty parts to the plant and hang them in the acid tanks and leave them for a while to clean them.



Sorry just reliving my youth.

 

[bax]

Good for killing rust, I like and use the product. it produces a lot of scale that you have to get off if you want a smooth paint job.

 

[75junebug]

See if you can find some CRC SP400 or Selig Linebacker in a can. this stuff is an O2 barrier as well as a moisture barrier, that "repairs" itself if its scratched or dinged.It does not covert rust, but it does seal it. I would brush off the scale and apply. I have been using this as an undercoating for all my vehicles for the last 15 years. It usually lasts 3-4 years before another application is needed. I sprayed it in every nook and cranny I could get to, including behind door panels. No new rust on my stuff, and I used to run the beach on Padre, and the back bay mudflats .

 

[cldonley]

I've used the Permatex rust converter on a lot of applications with great results. As far as whether it will continue to rust beneath, that can happen. Rust is oxidized metal; if oxygen is present, unprotected metal will rust. If you seal it up, it still may rust if the oxidizer is still present. You can slow it down, but the only way to stop it is to remove all the oxidized metal and then prevent further exposure (paint). One of the reasons our rigs rusted so badly is because the metal between the spot welds could trap oxidizers like water and salt between the spot welds and accelerate the process. If you do a good job with the wire brush and apply the converter you can slow the process way, way down.

 

[67RT]

Great. Just ordered some. I am a pharmacist and the colas are huge kidney stone formers due to the phosphoric acid.. Stay away..