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Topic Review (Newest First)
Today 09:27 AM
Chevymon
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.

Yesterday 07:18 PM
Old Fool 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
Yesterday 10:06 AM
zardiw 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
10-03-2012 05:54 AM
Lizer
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.
10-03-2012 12:34 AM
TARM 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
06-30-2012 06:25 AM
Lizer
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.
06-30-2012 12:37 AM
GypsyR 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.
06-27-2012 07:37 AM
sumner41
phophoric acid

Quote:
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.
11-19-2011 10:03 PM
Powork 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.
11-19-2011 08:11 PM
John68040
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.
11-19-2011 04:29 PM
deadbodyman 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....
11-19-2011 01:00 PM
Busted Knuckles Pretty interesting article on the subject: http://www.hotrod.com/techarticles/b...removal_guide/
11-19-2011 12:13 PM
Old Fool best rustconvertor for surface rust = convert it to dust, abrasive blasting is best.
11-17-2011 08:24 AM
Lonnie Jones
rust

I have used "Corroseal" for years both on cars and industrial equipment and it works. Do not sand blast, but knock off any loose rust with a wire brush. Apply "Corroseal" to rusted areas with a brush. Let it dry then apply sanding sealer and sand where necessary. I have used this on several cars I refurbished and have had very good luck with it.
I have been buying it from an industrial marine supple-house.
11-01-2011 06:20 PM
deadbodyman
Quote:
Originally Posted by TucsonJay
I don't personally use epoxy... so I don't have an opinion about that combination.

I would call a tech line, and speak to a company techie about it.
when you use an acid product (even etch primer) fillers (bondo) wont stick too well You can even blow the filler off with an air blower...epoxy sticks very well to it so you would want to treat the bare metal and rust then epoxy ,then use the filler on the epoxy.
Epoxy alone wont stop rust even if its wire wheeled and cleaned up well ....sand blasting might clean it up enough to use epoxy alone but personally I dont think its enough and to be totally honest I dont think the guys out in the dry desert climates or the guys that build the high dollar restos know for sure either since none of those cars ever see any weather and they are always in a garage and if ever driven only on the nicest of days.....I'll bet I can epoxy over active rust and put the car in the shop and it'll never come through either but leave it out in the weather and its a whole different story.
Just for the record using a pump spray bottle works fine (never use a paint gun) but use a paint mask with charcoal filters the same type you would use when spraying acid etch primer or todays paints..I would think just the label "ACID " would be cause for caution a reading the directions....
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