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Use of Ospho rust stopper product, then paint??

  
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Use of Ospho rust stopper product, then paint??

 
jbmacneil jbmacneil
Enthusiast | Posts: 518 | Joined: 07/09
Posted: 07/10/10
07:45 AM

Hey Guys, I have been using Ospho as a brush on rust preventative and it is like water.  It turns the bare metal a slight blackish tinge, and I have been told I can paint over it, but it leaves a not so smooth surface even after wiping. Does anyone have everience with this stuff and if so, what are the steps from applying the ospho (Cause it is good stuff) letting it dry overnight, to applying my Epoxy primer, then slick sand, then my Urethance Carosel Red!!!!  Thanks again all, as usual, youre all the best!!  JB  

Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 07/10/10
08:16 AM

I never paint directly over ospho.
I sand the surface after the ospho has died over night and then prime over the ospho.
Some spots that turn black should have a second coat applied to them.
It is good to etch non rusted metal as well.
I usually spray mine on out of a clean spray bottle.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

mb68bird mb68bird
Enthusiast | Posts: 468 | Joined: 06/10
Posted: 07/10/10
09:50 AM

Rust never sleeps, even if you coat it with something chances are it will bubble up the paint in that area.
Best to cut or at least grind away all the oxidation and build back up with weld and use a self etching primer.  

idrivejunk idrivejunk
Addict | Posts: 5000 | Joined: 12/09
Posted: 07/10/10
10:30 AM

Never used it.  
idrivejunk

Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 07/10/10
01:30 PM

Id it is like naval jelly but better.
Yes if badly rusted best to cut and weld in some new metal.
Ospho is better then self ecthing primer and is a self etching primer used it on all the cars I have done body work on and it has worked for years yes years.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

Mr.Milt Mr.Milt
Guru | Posts: 1135 | Joined: 08/08
Posted: 07/10/10
02:11 PM

Rust is my nefarious arch enemy so if you don't mind I'll add a little more to the string. Ospho, is a water based phosphoric acid solution and really intended to be used as metal prep. Acid will eat away rust. Many acids; like hydrochloric, and muriatic acid, will eat rust, metal, concrete, and you too. If you go down the strong acid road use extreme care and be sure to neutralize it. Phosphoric acid is relatively safe when it is diluted and can even be found in Soda Pop as well as Ospho and similar products.

Many rust removal products, like Ospho, leave behind a coating of Zinc Oxide or Iron Phosphate to prevent further rust.  Although you can paint over it you should probably sand lightly and remove the powder.  The "black stuff" is probably the result of rust conversion. Rust, Fe2o3, is that stuff that eats up metal. It can be converted to a more stable form of rust - i.e like gun bluing (I think chemically it is Fe2o4) and many products have a rust converter blended into them.  The big problem with rust converters is that the need some rust to work but on thicker rust they will only convert the top layer leaving some of the nasty unconverted rust under the black coating.

Grinding the metal to a bright shinny surface probably will not remove all of the rust either - but you may need an electron microscope to see it. You will certainly thin the metal. Bright clean metal is also susceptible to flash rusting, caused by the moisture in the air. That's why we use a metal preps like Ospho.

Despite the claims I wouldn't leave the area unfinished very long. BTW Normal primers are fairly porous and will not prevent further rusting.  Self etching primer followed by a coat or two of epoxy primer is much better but isn't perfect either - so a top coating, ASAP, is recommended.  

Now I will share my most secret secret. Don't tell anyone else - ever. If you really want to remove all of the rust use a process called electrolysis. You mix washing soda with water and suspend the part to be cleaned in the center of a container with wire.  Add a metal bar to the outside of the container and connect it to the positive terminal of a 12v DC power source (like a trickle charger).  Connect the Negative terminal to the wire holding the part you want to clean.

Electrolysis really works great but like anything it is not perfect. For one thing the process is line of site. If you put a complex part in the solution it will only remove the rust on the sides facing the positive terminal.  The process will remove chrome and other plating (it will even loosen paint); You may find the part is pitted after the rust is gone; You probably should clean the part and put on metal prep immediately after removing the part to protect it from flash rusting and prime/ paint it as soon as its dry; Finding a container large enough for a Catalina can also be a problem.  If you want to know more you can Google "electrolysis" and find all kinds of data.

Be safe,rust free, and live long an prosper.  

idrivejunk idrivejunk
Addict | Posts: 5000 | Joined: 12/09
Posted: 07/10/10
03:01 PM

Mr Spock, I mean Milt- What is washing soda? Baking soda?

+1 on your post. All very good points, especially about topcoating ASAP. Laugh  
idrivejunk

Mr.Milt Mr.Milt
Guru | Posts: 1135 | Joined: 08/08
Posted: 07/10/10
05:52 PM

Washing soda is a component of laundry detergent and you can usually find it where other laundry stuff is sold; and maybe a good hardware store.  You could also use Lye (drain cleaner) but a strong solution of it could burn you so Washing Soda is better. You really don't need a lot of it- About a tablespoon of soda to a gallon of water is good enough. Water is not a good conductor of electricity and the soda enhances the flow of current.  The process leaves the steal intact but it takes awhile. Be prepared to wait a couple of days, or so, for more heavily rusted parts.

I've only had one part I was unhappy with; but it was extensively rusted and when the rust was cleaned off there were pits in the metal.  I fixed that by copper plating - which after polishing off the copper left the pits filled and I was able to finish it to like new condition.

I often use and 30 gallon plastic tub for the solution and I make a sacrificial metal grid around the outside and bottom of the tub for the positive terminal. Since there are more straight lines to the positive side of the circuit I don't have to move the parts as often and I can do more parts at the same time.  

Obviously, you can't let the parts touch any part of the positive terminal grid. Rust will collect on the positive terminals and they will get pretty nasty, as will the solution. The parts will come out rust free but may have a black film on them that will wash off easily.  Make sure you dry them completely.

If you want to test this you could do it with a rusty bolt in a quart jar.  Try one with a nut rusted to it and you may find the nut comes off without too much trouble.  

idrivejunk idrivejunk
Addict | Posts: 5000 | Joined: 12/09
Posted: 07/10/10
08:35 PM

Wow, thats a heap o learnin'! I used to work around a plating plant but never delved into those type of processes. However I did catch on to the copper plating-as-a-filler approach. Sounds top-notch for rust war on removeable, unreplaceable parts. Interesting stuff, all new to me. Thanks for bustin a little knowledge upside my cranium, Milt  Wink  
idrivejunk

jbmacneil jbmacneil
Enthusiast | Posts: 518 | Joined: 07/09
Posted: 07/10/10
09:41 PM

Wow Guys, as usual, THANKS A WHOLE BUNCH FOR ALL THE INFO!!!! You are all the best.  JB  

jbmacneil jbmacneil
Enthusiast | Posts: 518 | Joined: 07/09
Posted: 07/10/10
09:43 PM

Hey Pontiac Man, what grit of paper do you sand the ospho off with?? I can apply my epoxy primer right on after I sand the ospho yes?? Thanks again my friend.  JB  

idrivejunk idrivejunk
Addict | Posts: 5000 | Joined: 12/09
Posted: 07/10/10
10:16 PM

I'm no Pman but I like to hit even clean metal thoroughly with 40 grit then a quick buzz with 80, both on a DA, before applying primer of any kind. Just my .02  
idrivejunk

Pontiacman8 Pontiacman8
Moderator | Posts: 5771 | Joined: 02/08
Posted: 07/11/10
07:23 AM

I usually use 80Grit on areas that had rust on them but if the metal is good and clean of rust then I use 120 grit.  
Engine builder,self taught auto body guy.
Horsepower sells engines and torque wins races

Pontiacman8
Pontiacman8
Pontiacman8

jbmacneil jbmacneil
Enthusiast | Posts: 518 | Joined: 07/09
Posted: 07/11/10
07:37 PM

Thanks Pontiac man, I appreciate it!! JB  

jbmacneil jbmacneil
Enthusiast | Posts: 518 | Joined: 07/09
Posted: 07/11/10
07:37 PM

Thanks Pontiac man, I appreciate it!! JB  

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