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I was at my local hardware store and saw this OSPHO rust converter. Has anyone used it? Does it topcoat good?

it's phosphoric acid, works fine if you follow the directions

Bill

Before jumping in with both feet, I would recommend looking at the complete paint job as a whole for inter-compatibility. Just because someone has used it with good results does not mean you will experience the same results if you are using different paint products. If there are compatibility issues with what you are spraying directly over the Ospho, there stands a good chance to risk adhesion failure and thus paint failure down the road. To my knowledge, both House of Kolor and SPI epoxy primers are not compatible, there may be others. So prior to using an Ospho type product, insure it is compatible with your primer you plan on using (verify to the product data sheets). Otherwise you may be money ahead to find another method of prepping the panel that won't cause adhesion issues with your paint.

It's main ingredient is phosphoric acid but it has added ingredients (which you pay dearly for)that might affect your final finish, as Robert pointed out. It is marketed as a paint prep. For parts de-rusting get the generic phosphoric acid.

I've never seen it before, just curious about it.

Hey Charlie, where do you get your "generic phosphoric acid"???

Denny G.

Denny - you might find it if you know anyone in the right industry, otherwise Home Depot paint dept has various brands of phosphoric acid [tile and grout cleaner] ... Ospho has about the same formula as any of them, around 85% phosphoric acid, around 15% water [otherwise the pure acid is a white powder] and a surfactant or wetting agent, which I'd suspect is sodium carbonate

Bill

I've been thru this a couple of time before Bill. I've got a bath with about three gallons of Behr concrete etch that I've stripped a bunch of stuff in. Behr changed their formula last year and took out the Phosporic Acid and the new stuff doesn't work at all on rust.

One of our members here was using Klean-Strip Phosporic Acid Prep & Strip that he got at Home Depot. His pictures looked like it left the metal with a fairly bright green stain. The Behr cleaner after rincing just left the parts with a very thin satin gray coating. I picked up a couple of gallons of the Klean-Strip last week but haven't had a chance to try it yet. The MSDS says the concentration is 35-45%. if it works as good as the Behr did I've got a BIG Rubbermade container I was going to put about tem more gallons in so I can clean some fairly large items.
Still won't be big enough to get the fender, hood or cab in thought, dang it!!!!

Denny Graham
Sandwich, IL
D

I remember your discussion about the Behr product Denny - maybe you could get the Klean-Strip up to 85% by evaporating out some of the water? of course then you'd need to buy twice as much

not clear why you'd use phosphoric acid, meant to be used as a wash, for a soak rather than using electrolysis to remove rust, which is way cheap and works so well

what I've been using now for phosphoric acid because it's readily available locally, is Metal Ready from POR15, intended to be used as a wipe and etch, but I've used Ospho with no subsequent paint problems - and either product after the electrolytic process

Bill

You can get 85% phosphoric acid from duda diesal.com in various quantities from a quart to 51 gallon drums

I gotta admit Bill, I've never tried the electrolysis method. The discussions pop up a couple times a month and when the do the opinions are all over the place, good, bad, slow, leaves residue that has to be scrubbed when it comes out of the bath, works with a batter, doesn't work with a batter, high current required, needed to have one of those big $200 gas station battery chargers, uses mole asses, laundry soap, borax, soda ash, baking soda, soda pop, and that's just a few of the things that I've seen posted.
The phosphoric I was using from Behr was fast, removes rust, removes plating such as zinc, nickel and cad. Leave the part in over night and even the paint will begin to flake off. Best thing that I've found in my 69 years and I've been playing with old rusty junk since I was just a sprout in diapers because of me pop and big bro.
And as you mentioned, out of the bath rinse it with a hose and it's ready to paint or plate. All of these parts went into the phosphoric for various times and came out ready to go the cadmium plater: http://www.pbase.com/dennygraham/image/133951157

And for some reason I don't seem to be as afraid to use this stuff as I am of muratic or sulfuric acids. From what I've heard dilute it down enough and you can drink it. Should be obvious that I never took a chemistry course and I don't understand acids or things like cyanide. I've had several very expensive plating kits form Caswell here for nearly a decade and I've been afraid to mix them up because I don't understand the chemistry, and have never gotten an answer to the question of, how to dispose of it when I want to. We have no city or county collection programs around here, guess most people just dump their hasardist waste in the drive or out on some back road. I just taint about to do that.

Duda, duda day!!! Yep, by the gallon it's pretty expensive, bout twice as much as Klean-Strip, but....Klean-Strip is half the concentration so I guess it comes out about the same cept for shipping. They also have a 15 gallon container which is food grade 85%, which would come out to $20 a gallon before you add in the truck freight charges, which I'll bet are a bunch.

Ok, gotta go, my paint should be dry enough for me to move my gravel pan back into the garage.

DG

yes Denny, diluted enough it's used in many food products, like Coke and other colas, which is why what's most common is "food grade" - some might say it's the part that rots your teeth, rather than the sugar

folks you've heard all those stories from about electrolysis are blowing smoke, it's a specific simple process, using a small amount of sodium carbonate [commonly sold as washing soda in stores] in water, and in a pinch sodium bi-carbonate can be used, although it is slower ... a molasses or vinegar bath is a different animal [acids], and the soda pop is just weak [food grade] phosphoric acid

try the real thing, it's easy and works well and comes clean with the same water rinse you use with the phosphoric acid, the only caveat about the battery charger to use is it can't be one of the fancy new ones that sense the battery condition, what you want is basically just a 12V power supply, no high current needed - I use a vintage little charger I've had for years that was previously used as a power supply for a mobile radio base station - 24 hours will take care of all but the worst corrosion, which may take longer - the nice thing is no worry about leaving it too long, no effect on the base metal unlike phosphoric acid

as for disposing of the solutions, I hope you don't think your phosphoric solutions and the residue in it is readily dumped anywhere - with the soda solution it's easy to filter out the particulate leaving a very benign sodium solution

Bill

No, when the bath peters out I'm gonna uncover it out back of the barn and put a good sturdy screen over it so no animals can get into it. When the liquid evaporates out I'll take it to my plater. I talked him and he said he can take the salts.
I guess one of these days I'll throw an old rusty iron chunk in and see how it works.
DG

I just want to second Squeeze on the electrolysis. I was intimidated a bit by the idea but once I decided to give it a small scale test in just a small wash basin I was sold. I live on a lake so am quite conscious on contaminates getting away from my work area. I look funny vacuuming the drive way after stripping and sanding but feel its the best I can do all things considered. If you want to give the electrolysis a try I'll post a link to the site that I found giving very good directions and info. I think the guy is an anthropoligist or something like that so he explains it for non mechanical folks.

post it CASO and lets see what he has to say. I"ve used it but just not pleased with the results. Obviously I'm to impatient??

it's everywhere Alvin, all the antique machinery and tool sites recommend it ...
the main place everyone references is here now [moved awhile back]
then there's a ton of repeats:
http://www.thepontiactransampage.com/rust.html
http://www.ehow.com/how_2180910_washing-soda-electrolytic-rust-removal.html
http://antique-engines.com/electrol.asp

someone even U-tubed doing the inside of a gas tank

and of course it's right here at home:
http://www.stovebolt.com/techtips/rust/electrolytic_derusting.htm

make sure you have the polarity the right way round for it to work well, and use washing soda rather than baking soda for speedier action

Bill

Thanks for the links Bill. I remember quite a bit of discussion over this a while back. I'm fairly sure I had it all hooked up and done right but just to darn impatient with it.
Lots of good reading though to refresh my memory.

OK, since were all on ACID or rather all tuned in to ACID in this discussion, I've got a question for the chemistry students out there.
Right now, as I'm typing, my acid Behr phosphoric acid bath it filtering down
through a 260micron filter. I'm trying to filter out the dirt, paint and what not
that's accumulated in the bath over the summer. I also wanted to so how much
of the original three gallons is still there, sofar it looks like I‘m gonna have about
2 ½ gallons out of the three.
My losses would be from two sources, one occurs when the parts come out of
the bath, get drained and rinsed. The other is thru evaporation even though its
covered 99% of the time except when I'm loading or unloading the parts.
What I'd like to know understand, is there any way I can test the bath to
see how acidic it still is???

The MSDS specified that it was a bit under 50 % concentration originally.

Tks,
Denny Graham
Sandwich, IL

What is/was its original pH?

Measure the pH with test strips, often available in a drug store (or fish-tank store).

Sorry, the chem lab that I took regarding converting pH to other concentration-measures was far too long ago.

http://en.wikipedia.org/wiki/Acid%E2%80%93base_titration

The pH value would also increase (acidity decrease) from being associated with more basic compounds placed into the bath.

Yes,,,,,,what was its original pH? I dunno, that’s why I came to you well educated guys, remember, I’m part of the toothless crowd.
But Litmus strips are only gonna tell me if it and acid, base or neutral aren’t they???? Looks like the phosphoric should be between 1-2.
Well I know one thing that it is still doing, it’s still dissolving the paper towels that I’m wiping the funnels and jugs off with as I‘m filtering it back into it‘s containers.
I’m trying the Kleen-Strip stuff right now also. I had the grill professionally stripped the fall of 2009 and have had it hanging from the garage ceiling. There are a bunch of very light rust spots on all the parts that I had stripped so I’m tossing them into the Kleen-Strip for a few minutes to clean them up and prep them for the primer.

Wonder if I can mix the Kleen-Strip Phosphoric with the Behr Phosphoric????

Denny Graham
Sandwich, IL

A litmus test uses a color scale that can tell you approximate acidity/alkalinity (on the 0 to 14 pH scale) - not just used to determine if you have a substance that is acid, basic, or neutral (unless that is the gradations of the test kit you use).

The sensitivity (and range) of the test-strip is a function of the choice of strips.

http://www.indigo.com/test-strips/ph-test-strips.html

I would not be mixing those chemicals unless I had a hooded exhaust cabinet (as found in chemistry labs). If both are just phosphoric acid, they should mix without a worry of putting off any other gases, except for the dangerous phosphoric acid fumes.

the more common industrial 85% solution should have a pH about 1.5, but when you're dealing with dilutions, and probable contamination [from your previous metal soaks], it can be messier [scroll down to Polyprotic Acids] - but it still doesn't necessarily tell you how strong it remains compared to the original dilution .... phosphoric will convert rust until the solution is gone

Bill

I think a Hydrometer is more what I should be looking for. The MSDS lists the Specific Gravity and that should give me an idea of how well it's holding up.

Specific Gravity (Water=1):
1.575 for 75% Phosphoric Acid
1.692 for 85% Phosphoric Acid
And yes Bill it does seem to still be working just fine, even after derusting a bunch of stuff. I'm sure it's loaded with cadmium and zinc from a bunch of striping that I did on radio chassis.


Run into a brick wall again. I’ve just hit another obstacle and have wasted most of the
afternoon and a good portion of the evening hours looking around home for ideas and
online for a solution.
I need a very long narrow container, 50” by 10” to 12” wide and about 6” to 8” deep for my acid bath so I can dip my grill bars. I’ve looked at every thing that the big box stores have for storage and there is nothing that long.
I don’t mind spending a few bucks for a container as I will use it in the future, if I live long enough.
I don’t really want to get into building a wooden box and lining it with visqueen for an acid bath. To much chance of springing a leak, so what I really need is a long, narrow, short Rubbermaid container with a lid.

All this work might be a wasted effort, don’t know if my grill is worth saving, whatca think? http://www.pbase.com/dennygraham/grill


Denny Graham
Sandwich, IL

doubt you'll find anything ready made those dimensions, but there's no reason 6 mil poly won't work fine, I've used it for tanks a number of times - if you're worried about poking holes get 4 year greenhouse poly, virtually impossible to tear it, should be available at any ag supply - or if you know any farmers that do silage, get hold of some silage bag film, it really is indestructible, would be fine in a trough made of heavy cardboard

Bill

Hummm I wonder if non-ferrous suppliers get some of the metals in long narrow crates that could be lined with poly. I seem to remember in my metal shop days that copper and brass came in crates we just chucked out.

Thought about a length of 10" or 12" PVC split in half to make a trough. A four foot
long half section would hold about eight or ten gallons but the stuff runs anywhere
from $25-$75 a foot and a cap for the end is in the hundreds of dollars.
So…………that’s out.

An ag dealer huh. Got lots of them out where I'm at half way between the lake and
the river. Looks like I might have to end up with some kind of trough like that after
all if I want to get this done. The only problem I see with that is it would be kind of
a temporary set up which I'd have to empty out a soon as I'm finished. I was sure
hoping to find something that was a little more sturdy or permanent with a fairly
tight cover that I could store the liquid in from one use to the next. That’s what I'm
doing now with the Rubbermaid storage containers that I've been using.
Well, I'm off to search the net for some info on "silage bag film", wonder how it
would hold up to phosphoric acid?????

Thanks for the ideas guys, been awake half the night hoping for an epiphany like I
had the other night. I’ve been hearing for years all the horror stories of days spent
taking the rivets out of the grills. I woke up in the middle of the night last week and
had my answer. I had this picture in my mind of those vise-grip pliers to hold a drill
bushing on center while drilling the rivets out of the grill. They worked great, I took
the whole grill apart in less than two hours (with several interruptions at that) and
didn't damage one of the original holes.
I’ve all ready talked to a machine shop about making a short run of the special hardened
drill bushings that holds the drill on the center of the rivet head and I‘m gonna search for
quantity prices for the vise-grips this week. I think anyone that’s tried to balance a drill bit
on four dozen spinning tubular rivet heads would be glad to have a pair of them in their tool box.

So, back on track for my orthophosphoric acid tubs.
Denny Graham
Sandwich, IL

Hi Denny,

Child's plastic wading pool?

Well, that's solved. Spent most of the day at AG stores and garden supplies looking for silage fabric or
planter liners. Only had 100 foot rolls or those 8'x60' silage bags. Finally gave in an came home.
I poured all the phosphoric I had (5 gallons) into the biggest Steerite storage container I had (34" long)
got a plastic brush and started soaking the bars down half at a time. Got them all cleaned up in a couple of hours.
Moving to the DP-90 epoxy primer first thing tomorrow if it's not raining.
Gotta call Hanson Rivet in the morning also and order tubular rivets, a squeezer and a squeezer dies set.
Hope to have the paint dry by the time the rivets get here from California, probably next week some time.
Now............on to the fenders!
Denny G