Ospho

[Burdar]

Ospho...never used it.  School me on uses and application methods.

I've got some scaly rust inside a convertible top frame I need to address.  My plan is to dip the header in EvapoRust to clean it out.  Once it's clean, would Ospho be a good product to spray inside or not?  I assume I could put it in a pump sprayer and shove the nozzle into the void to apply it?

[ek3]

phosphoric acid . converts iron oxide to iron phosphate . it also  contains a di-chromate to inhibit future rust... good product.  be sure to get it completely dry in recessed areas . plenty of air flow...  nothing beats zinc/ epoxy primers overall

[DeathProofCuda]

I've used it quite a bit over the years, although I typically only use it on stuff that is too large for me to soak in EvapoRust. 

[DeathProofCuda]

Is your intent to use it as a rust-inhibitor for an area that is not accessible to paint?

[Burdar]

Is your intent to use it as a rust-inhibitor for an area that is not accessible to paint?

Sort of I guess.  The front section(header) of a convertible top frame is hollow.  The only real access points to the inside are through the latch holes.   The outside is decent but inside has scaly rust.  The only way to clean it out is to dip it in a rust remover.  I found a deal on EvapoRust in bulk.  I'm going to build a trough and line it with plastic...then dip the header to clean out the rust.  Once the rust is gone I'll need to protect the metal some how. 

My thought was to just buy a half gallon of Rustoleum and pour it inside from a few different angles and hope that it coats the inside well enough.  Then I read a few posts about Ospho and thought that might work as well.  Maybe it would be a good pre treatment before pouring the Rustoleum?  I'm shooting blind here.  Looking for options.

[DeathProofCuda]

Is your intent to use it as a rust-inhibitor for an area that is not accessible to paint?

Sort of I guess.  The front section(header) of a convertible top frame is hollow.  The only real access points to the inside are through the latch holes.   The outside is decent but inside has scaly rust.  The only way to clean it out is to dip it in a rust remover.  I found a deal on EvapoRust in bulk.  I'm going to build a trough and line it with plastic...then dip the header to clean out the rust.  Once the rust is gone I'll need to protect the metal some how. 

My thought was to just buy a half gallon of Rustoleum and pour it inside from a few different angles and hope that it coats the inside well enough.  Then I read a few posts about Ospho and thought that might work as well.  Maybe it would be a good pre treatment before pouring the Rustoleum?  I'm shooting blind here.  Looking for options.

Sorry, can't offer much in the way of real world experience for that case.  As ek3 suggested, getting Ospho to dry in recessed areas (where it can pool) can sometimes be a challenge.  Given that the part you're working on is probably 50+ years old, had no previous rust prevention coating, and will likely be stored in better conditions for the next 50 years than the last 50, I probably wouldn't give it the belt and suspenders route (EvapoRust + Ospho + Rustoleum).  I'd probably opt for the EvapoRust + Rustoleum route.  Whatever you do, it will probably be better than from the factory.

[Bullitt-]

  I've tried the ospho type product but of long lasting protection I like this better..
Sold under many labels, converts rust to a black sealant that will last about forever if done properly..... Similar to the POR product but you can buy small amounts.
https://shop.advanceautoparts.com/p/permatex-rust-treatment-8-oz-81775/11082120-P

[ek3]

get some zinc chromate primer. ppg or sherwin williams sells an alkyd oil version... ospho wash it , then  thin it [zinc primer] with acetone pour it in let it dry ..done  it will even keep your battery post clean for 2+ years ! just coat the tops !!

[mopartaz]

I've used this on my truck frame , seems to be decent.



https://www.mrochem.com/BlackStar-Rust-Converter.html

[Burdar]

get some zinc chromate primer. ppg or sherwin williams sells an alkyd oil version... ospho wash it , then  thin it [zinc primer] with acetone pour it in let it dry ..done 

EvapoRust is on order so I'll derust the entire thing with that first.  Is the Ospho added protection after the EvapoRust bath or is it strictly for converting rusted metal?  I'll look into the zinc chromate primer.  Thanks

[ek3]

Evpo rust cleans it. ospho has di chromates [anti rust chems] and  can go on tight surface rust with no sanding at all . as long as you get any loose rust scale off the surface. it will convert and prep powdered rust and make it ready for painting ! i first used it 30+ years ago on military contracts ! it needs to completely dry to paint it . hair dryer or fan will do..

[gzig5]

I used Ospho on the old trunk pan and the bottoms of my extra doors.  You need to get loose scale off and I apply with a brush but spray might work. It dries to what seems to be a hard durable coating.  My wire wheel would barely touch it.  I will be using it on the roof support structure soon. 

[PLY474]

I haven't used it, but I hear that molasses and water removes rust from large parts, and on a budget.  The molasses can be bought from farm supply stores.  https://christinedemerchant.com/molasses-rust-removal.html

Once a year or so I shoot Fluid Film into the hard to reach areas of the car such as the quarter-to-outer wheel well seam.  It's active ingredient is lanolin (wool oil).  Smells a little weird, but once dry has no scent.  https://www.fluid-film.com/

Eastwood used to sell an aerosol cavity wax with a long tube applicator.  I don't see it now, but similar to this.  https://www.amazon.com/KBS-Coatings-75101-Cavity-Fluid_Ounces/dp/B00TVH7R5O/ref=sr_1_5?dchild=1&keywords=cavity%2Bwax&qid=1625108850&s=automotive&sr=1-5&th=1 

[ek3]

just wanted to let you all know this.. https://gulfcoastpaint.com/product/mcu-100-primer-finish-moisture-cured-urethane-aluminum-coating/  ----   this stuff is unbeatable at rust control . bare steel is coated with it , then they scratch the metal and apply salt spray test to it. no rust will form other than the bare scratched area . it sticks so tightly that moisture cant get to the steel to rust ! -0- migration of the rust ! and , it needs no top coat ! if you plan to paint over it , you have to do it before 24 hrs.. excellent for hidden hard to reach  areas that you want to protect from rust. this is not a body primer but an  excellent option for certain uses. ..... this is a good example of this stuff. -  > https://gulfcoastpaint.com/cant-abrasive-blast...