OSPHO and Cold Galvanizing Compound

[Gary Crehan]

I recently cleaned up my boat trailer and treated it with OSPHO which I have used before. I want to use Crown cold galvanizing coating. I called OSPHO and the tech I talked to said they had used a different type of rust changing material that was mostly tannic acid, I said OSPHO contains 45% phosphoric which is way more that what he had used. The paint peeled of what they had used. Has anyone used cold galv after using ospho. TDhe steel on the trailer seems to have a shiny looking surface now and I'm wondering If I should just wash it with soap and water, or use thinner or, well I just don't know. I need some help

 

[rlitman]

I thought Ospho had soap in it. I've had the best luck brushing it off with a steel brush and lots of water, followed by a thorough drying before painting.

 

[Gary Crehan]

That's the thing, paint is not a problem. The cold galv is 93% zinc. I'll have to try it.

 

[rlitman]

That's the thing, paint is not a problem. The cold galv is 93% zinc. I'll have to try it.

9x% zinc (the proportion varies) in powder form, but the rest is acrylic paint binder.

 

[Gary Crehan]

9x% zinc (the proportion varies) in powder form, but the rest is acrylic paint bind

Crown cold galv coating 93% zinc

 

[Gary Crehan]

I thought Ospho had soap in it. I've had the best luck brushing it off with a steel brush and lots of water, followed by a thorough drying before painting.

No it is a balanced formula of Phosphoric Acid, Dichromates, Wetting Agents and Extenders.

 

[rlitman]

...Wetting Agents...

And those are? My point about the percentage is that pretty much all cold zinc formulations work the same way. They're zinc powder and a binder.

 

[pooslet]

Used a lot of Ospho on offshore steel structures and equipment. Seldom used water following the 24 hour drying period since water pretty much neutralizes ospho before it reacts/dries. We would brush off the powder residue and clean the surface with paint thinner or reducer suitable for whatever paint coating was to be used. Quite often the primer coating was (rattle can) cold galvanizing, if we were not applying an engineered coating system.

 

[Gary Crehan]

Thanks that's what I was looking for. I can clean it a thinner.