Ospho VS. Evaporust

[pontiac428]

Ospho and Kleen Strip prep and etch are two products that have both changed formulation in the last few years. Ospho did most certainly have chromic acid in it at one point, I have some in stock still. I've also seen the newer SDS that says phos only. And Kleen Strip once was a 50/50 mix of hydrochloric and phosphoric acids, but now is only phosphoric. As a pickle and etchant, it's all fine and good. As a rust converter, straight phosphoric is better. As a post-parkerizing (manganese conversion) rinse, you really want the chromic acid. I like the new Kleen Strip because the old hydrochloric was in there more for the concrete prep use. I am sad about the new Ospho, the chromic set it apart in my opinion. Now, the two products are the same as far as I can tell.

The biggest impact on how fast these work is temperature. Concentration isn't very critical, so pour some hot tap water in a bucket and stir in your acid to about 20% v/v if you want it to work fast. It will.

 

[dabear3428]

i'm currently using both.
evaporust removes the rust, and will not change the dimensions of the work, phosphoric acid converts the rust and will change the dimensions.
Evaporust needs to be removed and the metal prepped for paint, phosphoric acid can be sprayed on let dry and painted over (acts as a primer/bonding agent).
if you want to restore a bare metal surface (like a lathe bed) use evaporust then clean and do rust prevention if you want to paint IMO use phosphoric acid.

if you want evaporust to work fast put it in a heated sonic cleaner, then it is fast.

they both stop rust very well it is just a question of what is next after the rust abatement, and evaporust is a lot more expensive i get 5 gal from my local auto parts store for about $100 and a gal of Phosphoric is about $30 but the gal of Phosphoric goes a lot further than the 5 gal of evaporust (depending on how deep the rust is).

 

[dabear3428]

These were a pile of rust after sitting is a bucket of water for coupe of years. no real cleanup other than dumping them into the sonic cleaner filled with evaporust and heated/agitated for 2 hours. keep in mind this depleted about 2 gal of evaporust so not cheap.

also phosphoric acid is much harsher, with the evaporust you can dump it on your grass after it is depleted (makes a good iron rich fertilizer), don't try that with Phosphoric acid.

 

[dabear3428]

If I'm not mistaken Ospho converts rust to an oxide, the others dissolve rust.

converts rust to iron chloride not Oxide that is what you started with, iron oxide or "rust"
and yes evaporust is a kelating agent and it basically pulls the iron out releasing the oxygen, this keeps the iron in the solution. evaporust just leaves the pits behind that the rust made in the part but does not affect the surface that is not pitted, as such it is good for removing rust from lathe beds leaving all of the original machined surfaces (less the pits)

in my experience evapo rust leaves a sticky film on the parts but i think that it retards further rust formation, i sometimes clean it off and some times not depending on what it is on.

Evapo rust IS Not Acidic or Basic it is neutral.

the phosphoric and evapo rust are self limiting, ie the part can just sit in evapo rust and the process stops when the rust is gone, with the Phosphoric acid the way i use it, it dries and the process stops.

 

[woodchucker]

i'm currently using both.
evaporust removes the rust, and will not change the dimensions of the work, phosphoric acid converts the rust and will change the dimensions.
Evaporust needs to be removed and the metal prepped for paint, phosphoric acid can be sprayed on let dry and painted over (acts as a primer/bonding agent).
if you want to restore a bare metal surface (like a lathe bed) use evaporust then clean and do rust prevention if you want to paint IMO use phosphoric acid.

if you want evaporust to work fast put it in a heated sonic cleaner, then it is fast.

they both stop rust very well it is just a question of what is next after the rust abatement, and evaporust is a lot more expensive i get 5 gal from my local auto parts store for about $100 and a gal of Phosphoric is about $30 but the gal of Phosphoric goes a lot further than the 5 gal of evaporust (depending on how deep the rust is).

yes, but the evapo rust can be re-used, the phosphoric acid is a one time brush on or spray on.
I have no problem painting after evapo rust. I clean it off with water, and use tsp before painting or mineral spirits. either works.

No I have not painted over phosphoric acid... good to know. But how do you stop it from being an acid if you just paint over it. I would think you would want to neutralize it.

 

[Advil]

Love Ospho. It has nothing to do with Evaporust.

I primarily use Ospho convert rust and keep things in decent shape that have to sit outside. It's a great product when you want to put out minimum effort and just stop some rust. A couple days ago I used it to convert the rust on an old brush hog... very quickly took a wire wheel to whatever paint and rust bits were super loose then quickly painted Ospho over the whole thing because I don't care about the paint anymore. It doesn't instantly attack adhered paint but it would be bad news for a high quality painted surface. Mainly, if it's rusting, you can slap on Ospho which has the consistency of water and the surface will do pretty well for a couple of years in the weather. You'll see it change from rust color to grey or black almost immediately.

While you can do a rattle can paint job over Ospho it won't be really pretty. If you are trying to do quality paint you need to wash off the Ospho with soapy water while it's still wet. This means if the Ospho has completely dried and you want it off you need to quickly brush on a tiny bit more so it's damp looking again then wash it off.

Things you don't need to wash it off of: Tractor Implements. Exposed outdoor steel frames and boxes. Rusty nuts/bolts. Old tools that just need to stop rusting and not look brown.

When you must wash it off: Anything that needs an automotive quality paint job. Also speaking from experience if you use it on an old wood stove, best to wash it off if you want a really nice paint finish for inside your home.

EDIT - 1 Gallon of Ospho would be a near lifetime supply for anyone who doesn't use it constantly. It goes a very long way. My current gallon is pushing 20 years old and is only getting down to the bottom now.

As opposed to actually removing rust from parts using the more mild Evaporust. Works good, when you want to take the rust off something, but in my experience the stuff doesn't really last a long time like some suggest. A couple of really rusty cruddy parts and it doesn't work that well anymore. And it's too expensive to buy 5 gallon pails of it. I'd rather use vinegar or electrolysis or something for $5 and not worry about trying to make the solution last.

 

[dabear3428]

yes, but the evapo rust can be re-used, the phosphoric acid is a one time brush on or spray on.
I have no problem painting after evapo rust. I clean it off with water, and use tsp before painting or mineral spirits. either works.

No I have not painted over phosphoric acid... good to know. But how do you stop it from being an acid if you just paint over it. I would think you would want to neutralize it.

evapo rust can only be reused until it becomes saturated and then it will not work anymore.
a little Phosphoric acid goes a loooooooooooog way. in most cases just apply it (i found that a small spray bottle puts it on really well and then just let it dry then paint. for heavier rust you may need two coats applied and may need to brush off a white film and then wipe down with mineral spirits then paint, (I never needed this)

OSPHO is a balanced formula of Phosphoric Acid, Dichromates, Wetting Agents and Extenders. Ospho is environmentally safe and non-flammable. OSPHO seals out moisture and prevents future rust from forming. OSPHO can be applied to just about any rusted or steel surface including: Vehicles, Trailers, Fences, Iron Railings, Sheet Metal, Outside Tanks, Lawn & Farm Equipment, Marin Applications and more. OSPHO is primarily used for bars-metal applications but can be used painted surfaces as long as the quality of the paint is not compromised. OSPHO isrecommended for use under oil based primares or paints. Test trial samples before using Epoxy or other paint systems. A paint job will last much longer afetr an application of OSPHO because subsequent paint coatings attach themselves so tightly that moisture and oxygen cannot attack the metal. OSPHO is water thin and therefor covers a larger area ten painrt and goes on easily. OSPHO is easily effective for exterior and interior work alike. OSPHO safely dissolves bleeding rust from many painted surfaces. For best results, use OSPHO at temperatures no lower than 36°. Excess dew and humidity may prolong drying time, cause a reoccurrence of the drying process resulting in a powdery buildup. Spray equipment should be flushed out with water after using. Clean brushes with water. Avoid spreading OSPHO on adjacent areas such as concrete, masonary and stone work as it will etch/bleach almost immediately.

RUSTED METALS - OSPHO is a rust-inhibiting coating - NOT A PAINT You do not have to remove tight rust. Merely remove loose paint and rust scale, dirt, oil, grease and other accumulations with a wire brush or pressure washer and let dry - apply a thin coat of OSPHO as it comes pre-diluted in the container. Let dry overnight for a minimum of 24 hours, then apply whatever paint. Longer dry times may occur depending on temperature, humidity and over-application of product. OSPHO has the consistency of water and treats up to 600 square feet per gallon. When applied to rusted surfaces, OSPHO causes iron oxide (rust) to chemically change to iron phosphate - an inert, hard substance that turns the metal black. Where rust is exceedingly heavy, two coats of OSPHO may be necessary to thoroughly penetrate and blacken the surface to be painted. A dry, powdery, grayish-white surface usually develops when cured. Brush off any loose powder and wipe down with Mineral Spirits before painting.

NEW METALS - For new ferrous metals: remove dirt, grease, or oil; apply OSPHO in a thin coat, let dry for a minimum of 24 hours, then apply paint. Longer dry times may occur depending on temperature, humidity and over-application of product. A dry, powdery, grayish-white surface usually develops when cured. Brush off any loose powder and wipe down with Mineral Spirits before painting. OSPHO penetrates deep inside of the metal's pores to convert and protect before Iron Oxide is present.

 

[dabear3428]

Love Ospho. It has nothing to do with Evaporust.

I primarily use Ospho convert rust and keep things in decent shape that have to sit outside. It's a great product when you want to put out minimum effort and just stop some rust. A couple days ago I used it to convert the rust on an old brush hog... very quickly took a wire wheel to whatever paint and rust bits were super loose then quickly painted Ospho over the whole thing because I don't care about the paint anymore. It doesn't instantly attack adhered paint but it would be bad news for a high quality painted surface. Mainly, if it's rusting, you can slap on Ospho which has the consistency of water and the surface will do pretty well for a couple of years in the weather. You'll see it change from rust color to grey or black almost immediately.

While you can do a rattle can paint job over Ospho it won't be really pretty. If you are trying to do quality paint you need to wash off the Ospho with soapy water while it's still wet. This means if the Ospho has completely dried and you want it off you need to quickly brush on a tiny bit more so it's damp looking again then wash it off.

Things you don't need to wash it off of: Tractor Implements. Exposed outdoor steel frames and boxes. Rusty nuts/bolts. Old tools that just need to stop rusting and not look brown.

When you must wash it off: Anything that needs an automotive quality paint job. Also speaking from experience if you use it on an old wood stove, best to wash it off if you want a really nice paint finish for inside your home.

agreed if you want a nice finnish you need to take further steps but for what i'm using it for as long as it is not rusting anymore and all one color that is all im looking for.
the rust that it converts leaves a bumpy surface and would not be my choice for a show car finish but the paint sticks to it better than bare steel. adding a primer coat is better but paint right over it as a primer works well also.
I use it on tractor implements and it will work with out paint but better to put paint on it for longer term protection. you can take rusty oilfield pipe lightly brush it and spray it down and it will be black/gray and wont rust for a long time out in the weather.
to be clear it stops the rusting, converts the rust to a stable material to be covered or not with paint. it is not magic and will not do anything for the pits and bumps created by the rust in the first place. evapo rust does take off the bumps but also leaves the pits.

 

[Dabbler]

EDTA is a little slower than evaporust, but considerably cheaper. I use citric acid for a first pass because it is even cheaper and readily available. I then skip the EDTA and do a short pass in evaporust. Evaporust is way too expensive to do the whole job.

I stay away from muriatic acid as it etches the metal - i suppose it could be used topically rather than dip, and for a very short time only.

 

[woodchucker]

EDTA is a little slower than evaporust, but considerably cheaper. I use citric acid for a first pass because it is even cheaper and readily available. I then skip the EDTA and do a short pass in evaporust. Evaporust is way too expensive to do the whole job.

I stay away from muriatic acid as it etches the metal - i suppose it could be used topically rather than dip, and for a very short time only.

never heard of it before. I see it's a medical chelation chemical.