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  #31 (permalink)  
Old 11-19-2011, 02:00 PM
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Pretty interesting article on the subject: http://www.hotrod.com/techarticles/b...removal_guide/

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  #32 (permalink)  
Old 11-19-2011, 05:29 PM
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Whats best in my opinion is use both together... blasting AND Ospho...
Its my opinion that even if you blast, the rust its still there on a microscopic level....The reason I feel this way is when a pitted piece of steet metal is blasted and set out in the weather unprotected ,the pits always start rusting before the unpitted metal...
Thats where the Ospho comes in...Imediately aftre blasting I treat the whole car and let it dry not only will it kill the rust on a microscopic level it'll protect any unrusted sheet metal from getting surface rust as long as the cars is in a garage surface rust wont ever be a problem.
Ospho is easy enough to use and "Does Not Need To Be Neutralized"

Blasting is a good way to remove rust but only if you take the car completely apart for a total restoration... chrome ,glass,REGULATORS,complete interior inc. dash,complete drive train....NO way you would do it on a car your driving and just doing a weekend floor job. Or a vinyl top repair job. Or even in places like a windshield frame only repair ,where its only pitted rust but its structurally sound the glass is out but it's a nice running car thats being driven ... no way you would want to blast there ....Sure You might be able to turn a minor in and out repair job into an unneeded,all out total resto but most guys cant or wont pay 50,000 and up and something that looks nice already.. Again thats where "Removing" rust with Ospho and wire wheels is the best way I've found..
Yes..I went out and bought a blaster in fact I have three blasters at my shop A big commercial which I seldom use ,a small pressurized one that I use rarely but twice as much as the big one,and the small recyclng spot blaster which I use a lot (I'm on my third one) it makes almost no mess....

So its like the old question :whats the best seam to weld? butt,spot or flange....The true and only REAL answear is there ALL the best... when used where they're supposed to be.....You need to know them all and where to use them...
Many pros CLAIM blasting is the ONLY and best way to remove rust and strip paint....
Well ,I'm a pro too ,35 yrs exp... and I say its absolutly not...I know rust,I'm from NY where new cars get holes within five years ,I work with it almost every day....Even if I blast a car it gets Ospho.
using them together is the BEST way .....but its rare that blasting is a good option.. and never EVER a good way for anyone but experianced professionals to strip paint with...and dont hire a a man that blasts bridges to do your car on the side either, get someone that does automotive blasting.....
If you want to blast some rust yourself ,I strongly suggest you only use a recycling spot blaster...anything else and you have a 90% chance of doing expensive damage to the sheetmetal...or a motor (that sand gets everywhere ,places you would never expect or even think of like defroster vents or the fan ,you would find out when your cars finished and your driving down the road and turn on the defrosters and get a face full of sand.
AS for stripping paint .....if theres to much paint to sand off fairly easy (with 80 DA and do a whole car in a day or two) chemical stripperis a very good option (mabee the best) especially for the non-pros that want to remove a lot of paint fast...... all you need to know is a few tricks and tips and anyone can do it quick,neat and fast....My wife can strip a car and do it well...
.......She anit a professional stripper either....

Last edited by deadbodyman; 11-19-2011 at 05:47 PM.
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  #33 (permalink)  
Old 11-19-2011, 09:11 PM
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Quote:
Originally Posted by Busted Knuckles
Pretty interesting article on the subject: http://www.hotrod.com/techarticles/b...removal_guide/
Rust Bomb sounds like the best option I've heard so far. Actually removes the rust and sounds like it's a thick enough gel to use on the floor from underneath the car.
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  #34 (permalink)  
Old 11-19-2011, 11:03 PM
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also been using Ospho for years, depending on the job, but most any time on large bare metal areas with very light rust I will apply. I have found that you really need that light rust to convert/neutralize for a lasting coating.
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Old 06-27-2012, 08:37 AM
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phophoric acid

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Originally Posted by John68040
So would you recommend stripping to bare metal, treating with phosphoric acid, then using epoxy?
Absolutely correct. Our world is filled with magic potions. To do metal and paint work CORRECTLY, one MUST understand chemistry and metalurgey. RUST IS A CHEMICAL REACTION. METAL PREP is the way to go.
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  #36 (permalink)  
Old 06-30-2012, 01:37 AM
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Some lack of understanding here. I'm no paint and body guy but I know you don't "neutralize" acid with water (as keeps getting brought up). You can dilute it or rinse it away with water. To neutralize it you'd have to counter it with an alkali like baking soda or soda ash. In practice, the reaction between it and rust sort of "neutralizes" its acidic properties. (OK, not really neutralizes it. Re-read your old high school chemistry books for what is really going on.) The residue left after treating with phosphoric acid is mostly ferrous phosphate which has a mild rust retardent effect. Phosphoric acid combines so readily with water that any residue is easily rinsed away. As for whatever other additives may also be in the mix, I have no idea what they might be but I suspect it's best they be washed off. Scrubbed off, if need be. Below 94 degrees and once the water has evaporated out of it, fairly pure phosphoric acid returns to its natural state. That of a whitish solid.
Stuff like Ospho containing mostly phosphoric acid is meant to be a rust remover/metal cleaner. As such it pretty darn good stuff and has long been used by steel mills for that purpose. The rust "converter" stuff I've seen (and tried) is pretty interesting but is pretty much a band-aid. It stops the rust, for a while, and does a pretty good job of covering it up. Also for a while. Sooner or later the rust alway seems to come back through the "converted" area. Or did when I tried it anyway.
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  #37 (permalink)  
Old 06-30-2012, 07:25 AM
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Quote:
Originally Posted by GypsyR View Post
Some lack of understanding here. I'm no paint and body guy but I know you don't "neutralize" acid with water (as keeps getting brought up). You can dilute it or rinse it away with water. To neutralize it you'd have to counter it with an alkali like baking soda or soda ash. In practice, the reaction between it and rust sort of "neutralizes" its acidic properties. (OK, not really neutralizes it. Re-read your old high school chemistry books for what is really going on.) The residue left after treating with phosphoric acid is mostly ferrous phosphate which has a mild rust retardent effect. Phosphoric acid combines so readily with water that any residue is easily rinsed away. As for whatever other additives may also be in the mix, I have no idea what they might be but I suspect it's best they be washed off. Scrubbed off, if need be. Below 94 degrees and once the water has evaporated out of it, fairly pure phosphoric acid returns to its natural state. That of a whitish solid.
Stuff like Ospho containing mostly phosphoric acid is meant to be a rust remover/metal cleaner. As such it pretty darn good stuff and has long been used by steel mills for that purpose. The rust "converter" stuff I've seen (and tried) is pretty interesting but is pretty much a band-aid. It stops the rust, for a while, and does a pretty good job of covering it up. Also for a while. Sooner or later the rust alway seems to come back through the "converted" area. Or did when I tried it anyway.
THANK YOU. I've said the same thing here before, as well. Water itself tends to run a mildly acidic pH (around 6.8 if not ultrapure). Adding water to acid (note if you were in my laboratory you would NEVER be adding water TO acid) merely reduces the molarity of the acid. Weakening the concentration of the acid, yes, neutralizing it? Of course not.
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  #38 (permalink)  
Old 10-03-2012, 01:34 AM
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I am brand new here but this topic caught my eye as I am about to deal with some surface frame rust and some very light surface rust on the back of a door panel and body support on a Excursion. I have read every post with great interest.

What I have gathered from reading everything here is the following:

I see little controversy on here that Ospho does a good job of protecting or converting rust.

It seems the main and really only point of contention is whether Ospho leaves an acid film or not. Now specifically to this thread its a bit more detailed. We are speaking specifically if there is an acid film left when following the direction and procedures as laid out by DBM.

Is there some reason you can not just use a 0-14 PH testing strip on the metal surface after all the steps DBM does prior to spraying primer and see what you get?

Seems like a really simple and 100% way to put this to bed. I can not see how there could be any argument if the PH comes back somewhere around in the middle of the PH range. A 85% Phosphoric acid solution has a PH of about 0.5 PH so we are not talking some small change here.

My bet is that there is a differnce between Ospho leaving a acid film after dry vs following DBM steps and procedures there is an acid flim left from Ospho once you reach the primer spray step.

Basically it seems to me there can easily be a difference between soaking the metal with Ospho letting it dry

Now ready for epoxy primer and checking the surface PH

VERSUS

Soaking the surface with Ospho waiting wiping away any pools or drips any excess at all with a towel.

Waiting 24hrs

Sanding or scuffing the entire surface

Wiping off clean with a rag soaked in wax & grease remover (I think this may have a big effect)

Allowing to dry

Now ready for Epoxy Primer and testing surface PH level.


Its seems pretty straight forward and definitive to me but I am about as novice to painting as can be. Tons of experience Hot Parkerizing/Phosphating firearm parts for years but automotive industrial painting and prep Nope NADA NOT.


This looks like a much better choice for a person like me than a first time hobbyist than many of the other options out there. It will allow me to do sections at a time as I can. I can get it into hard to reach areas as taking some of these body panels off is not possible and or way to much involved for a daily driver. I just want to put to be sure I will not find a rotted out body panel under the undercoating in a few years. I live in the mountains of VA ( well we call them mountains here on the east coast) so we see salt and wet salt solution road prep during the winter months. I need to get the under carriage exposed surfaces sealed from this attack as best as I can.


DBM,

I want to personally thank you for spending so much of your free time attempting to educate others on the system you have used and found to work well. I have found it very helpful. But then I am very good at following directions. LOL
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  #39 (permalink)  
Old 10-03-2012, 06:54 AM
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Quote:
Originally Posted by TARM View Post

Is there some reason you can not just use a 0-14 PH testing strip on the metal surface after all the steps DBM does prior to spraying primer and see what you get?
Yes; pH strips require full immersion in the solution for which you are testing the pH and they need to be completely wet. Touching it to the metal would not give you a good reading.

Quote:
Seems like a really simple and 100% way to put this to bed. I can not see how there could be any argument if the PH comes back somewhere around in the middle of the PH range. A 85% Phosphoric acid solution has a PH of about 0.5 PH so we are not talking some small change here.
You're only looking at pH and not chemical compatibility.

Quote:
Wiping off clean with a rag soaked in wax & grease remover (I think this may have a big effect)
You would have to clean the metal with wax and grease remover anyways. But it's nothing I count on to neutralize an acid.
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Old 04-16-2014, 11:06 AM
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The best rust converter is Rust-X. Have used it for years and it works like a charm. Good idea to paint over it afterwards: Rust-X.com
I have also poured about a half 16 oz bottle into the radiator. It will convert all the rust inside the engine.....Probably a good idea to flush it afterwards since it is a weak acidic solution and could have an effect on aluminum parts.........I've poured it on aluminum and there does not seem to be any reaction.....so it's probably OK to leave it in, since it will be very diluted anyway.


z

Last edited by zardiw; 04-16-2014 at 11:17 AM.
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  #41 (permalink)  
Old 04-16-2014, 08:18 PM
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If you have your heart set on using a rust prep type product I would suggest you check out MasterCoat products. They have a very impressive product used on subway cars and bridges and holds up quite well.

This is the only system that I would trust other than abrasive blasting and epoxy.

Click here for MasterCoat System
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  #42 (permalink)  
Old 04-17-2014, 10:27 AM
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Quote:
Originally Posted by TARM View Post

What I have gathered from reading everything here is the following:

I see little controversy on here that Ospho does a good job of protecting or converting rust.

It seems the main and really only point of contention is whether Ospho leaves an acid film or not. LOL
I think that most here will agree that converting rust is not a good idea, what you want to do is remove rust. And some, if not most, will agree that phosphoric acid is a good way of doing that, but the point of contention from the paint manufacturers is only that it be thoroughly rinsed off. In fact a lot of them have an epoxy that is recommended to be used after metal prep, for better adhesion.

SPI does not recommend using a metal prep, but they do say its alright if you know how to paint prep the panel after its use, which does not include neutralizing in the technical sense.

This part that I posted earlier in the thread was cleaned by blasting then phosphoric acid and rinsed. This has been zoomed in quite a bit, the raised part at the bottom is actually only 1 1/2 inches wide. I have found that if I agitate the the thoroghly wet acid on the panel with a scuff pad or brush just before rinsing, it comes off like this. This was badly rusted as you can see by the pits.

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  #43 (permalink)  
Old 04-18-2014, 10:13 AM
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That master stuff only lasts a year......RustX has lasted many years on parts and other things I've applied it on.

The thing with rust removers, sand blasting, etc is that steel will start to rust IMMEDIATELY....so when you paint what you think is clean steel, that rust will eventually increase under the paint, or on the sides, and you will be back where you started.....

Makes a lot more sense to turn the rust into a protective coating that will never rust again.......

z
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  #44 (permalink)  
Old 04-18-2014, 09:33 PM
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Ospho does leave a protective film, that's the main reason I use it, so my bare metal does not rust...
Ospho does remove rust but it also converts rust {I don't convert I remove it) however I do believe converting it on microscopic level is a good thing...So even if I media blasted I'd be using Ospho...
I'm going to go out on a limb here and say I truly believe that even if you blasted the rust off, using Ospho is a better way than blasting and just priming.. Otherwise I wouldn't still be talking about it after all these years...I understand that others have had some problems and its always adhesion problems related to the way the metal was prepped prior to epoxy...Sure the simple cure is NOT To use Ospho if you don't want to take the time to do a proper prep simply epoxy over the bare metal and no adhesion problems...but your just swapping out adhesion problems for rust problems sometimes in less than a year...
Here's something you can try that always impresses me. sand some metal with 80 until you think its clean and ready to prime...then get the metal nice and wet with Ospho and scrub it in good with a red scotch brite and watch how much dirty grime comes off that metal that you thought was clean...
After the Ospho drys 24 hrs sand with 80 and then 180, I even go to 320 sometimes because after sanding with each grit it looks better and better ,theres no doubt which is cleaner just 80 grit or Ospho and 80-180-320,its like night and day.so give it a try and you decide whether or not its worth all the extra work.....Its only a foundation...
I have changed my procedure slightly now I use both water born AND solvent based Wax & grease removers before my epoxy ,I really like this waterborn stuff SPI has now...
To put this all in a nut shell,I think If there wern't any scary adhesion problems everyone would be using Ospho without a second thought just like I do.
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  #45 (permalink)  
Old 04-18-2014, 10:58 PM
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I have to agree with DBM on this. In my experience, you can sand off surface rust, wire wheel it, aggressively scrub with a stiff stainless steel brush, and ospho, or any other phosphoric acid solution, and have what is generally considered treated, or converted rust. the black or very dark colored stuff.
If you take a small carbide burr, on the black stuff, in the bottom of the pits, or wire wheel it again, aggressively, you will find red rust under the converted black stuff.

Rust is an electrolytic reaction. Take two different metals, put them in an acid solution, or a base solution, or a salt solution, and connect them to each other, one metal will be eaten away. Once steel starts to rust, you have the two different metals. The rust, and the non rusted steel. Add moisture and the rust feeds itself on the bare steel.
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