So I sprayed a half gallon of the strong 80% phosphoric acid (Food Grade) - to convert the iron oxide into Ferric Oxide.
Why? I already did a gallon of the 50% phosphoric acid - but I did it on the sly - on a back gravel road that is public - and I didn't take the time to really spray it well. Or at least when I checked with the inspection camera - it only seemed a little better.
So then I went to my relatives - so I could really devote more time - to really try to saturate the internal frame - with the really strong 80% phosphoric acid.
Since it's a horizontal surface - I'm concerned - but the rust is strong - so it should not just eat through the metal. That may have happened on the back tailgate - when I used the strong 80% phosphoric acid last year and now I had to replace a big part of the rusted out tail gate. More likely it was "rust creep" since I used an enamel paint that does not breath - and the car paint was a gloss paint also.
Anyway so I also tried out this new Epoxy paint last night - the fumes were really toxic. It's a lacquer epoxy "extreme chassis" paint. It takes a long time to cure - it's still sticky.
I better go wipe of the strong phosphoric acid off that new paint.
I'll check out the internal frame tomorrow - with the inspection camera.
The strong phosphoric acid took off some of the paint but not all of it - as I tried not to spray it on the new paint section. It was a thin layer of paint but that paint has a lot of particles to it or whatever.
So I think that layer still has paint to it.
Extreme Chassis Black has 3X the resins of traditional coatings, so it's tough enough for any undercarriage component...choose satin or high-gloss.
I just got a spray can. So I'll do another layer.
I'm focusing on where the LIFT goes under the frame because that's where the paint got scraped off before - from last year's paint job - so I had rust on the bottom of the sub-frame or chassis. So I converted that rust with phosphoric acid and painted on rust converter paint. Then I painted on etching metal primer because Rustoleum said to NOT paint the enamel directly onto the rust converter - the acid in the paint will destroy the enamel paint. Then I put another rust converter layer on - since the Extreme Black Chassis says NOT to be put on the "etching primer." oops. haha. THEN I put on the Extreme Black Chassis - and it didn't cure yet.
If you can keep the acid on it and continually wet, and soak for many hours. It will help as long as you flush it out.
https://www.wranglerforum.com/threads/phosphoric-acid-inside-frame-for-rust.2374955/
Anything you spray internally on the frame will attract dirt.
I suppose if it is paraffin wax...?
muratic acid is way more aggressive an acid, not only that it also eats clean metal and will continue eating metal unit it is neutralized.
https://forum.ih8mud.com/threads/phosphoric-acid-rust-removal.530408/
The stuff in the photo wasn't even responding to the wire brush in a 4" grinder. All the grinder was doing was shine the rust. Given enough time I'm sure it would have worked but the Prep & Etch at HD works MUCH faster. It's still not quick but it's the only thing that works for me.
exactly!
The directions say full strength on rust as heavy as I have
OK well I have heavy rust so!!
When applied to rusted surfaces, it resists/retards rust in chemical change on drying to a tough, hard surface ready for priming.
So I drove around for a half hour to help dry the stuff.
if you were to chemically remove your rust, a few things happen.https://www.motorgeek.com/viewtopic.php?p=453233
first and foremost you can have the de-rusting agent (acid) trap itself in nooks and crannies and make for a nasty friend that shows up later on when you dont want them too. i have had this happen a few times in parts that i acid dipped that i should not have.
now that said, I often use hydrochloric acid 20% with water as my de-rusting agent. It is quite aggressive, but gets the job done in a reasonable amount of time. I did acid dip some sheet components and have had the acid trapped in between layers like metal folds, seam welds, laminations, ect... not a good thing.
the third reason more closely has to deal with stresses... generally on a part when it is made the most beneficial stresses are compressive stresses. if a part has been corroded and then a chemical attack has been placed on the part it is very likely you just removed 2-3-10 thou of said part. by that time you could very well be below the as produced compressive stresses and be at the normalized or even tensile range depending on how your part was made. Do not forget that while your corrosion may have brought you to the normalized region in surface stresses, you may be making it worse off by chemically removing said rust!!!
http://scienceline.ucsb.edu/getkey.php?key=1933
Acid can dissolve the rust (Fe2O3). However, the acid will also oxidize the metal further, forming more rust, and dissolving that rust. In the simplest case, lets imagine hydrochloric acid and iron (HCl and Fe). When HCl encounters iron, whether it is oxidized iron (Fe2O3) or metallic iron (Fe), it wants to form iron chloride (FeCl2 or FeCl3). Therefore, when acid reacts with metal, it tends to dissolve both the rust and the metal, in order to form the iron chloride. However, if you were to carefully use dilute acid, you could dissolve away the rust before dissolving the metal.
Some acids remove rust (oxides), while others cause rust. Most acids will etch metal whether they cause rust or remove it. Phosphoric acid (H3PO4) is one type of acid which removes rust by converting it (iron III oxide) to a form which can be dissolved in water. Most other strong acids cause rust.
https://classicoldsmobile.com/forums/paint-70/phosphoric-acid-rust-removal-50584/
all of the common "MetalPrep," "MetalReady," etc. surface treatments are essentially phosphoric acid solutions +/- a bit of one thing (like hydrochloric acid) or another.
- Eric And also these are rather weak for removing rust. They also etch your parts for painting - their primary use.
heavier rust in a few hours. This is a more concentrated acid and MUST be washed off well afterwards.oops.
No way for me to wash off the internal frame.
Dissolves the rust in half the time as the store types Rated 1# in Military Vehicle Mag.
So it must be the 80% concentration instead of the store version that's 40%.
The problem is,if you acid them,they will rust if you don't put a rust protector on the parts.
https://eoncoat.com/eoncoat-science-technology/iron-phosphate-layer/
Iron Phosophate Layer
As EonCoat is spray-applied onto carbon steel, the acid in EonCoat converts the top layer of steel into an inert iron magnesium phosphate so that the steel can no longer corrode. This is the first line of defense EonCoat delivers. When this alloy layer is viewed through an electron microscope, it shows a thickness of 2 microns. Clearly visible in the electron microscopy is the chemical bond that results from the steel coming into contact with the patented acid formula in EonCoat. The resulting alloy is a permanent protective layer against corrosion.
OK so now I'm not worried - this is precisely what I did to the internal frame!!
An amorphous alloy layer of iron phosphate forms. This contiguous phosphate layer is created through a chemical reaction with the steel–the EonCoat and the steel share ions and the EonCoat chemically becomes part of the steel. There are no coverage gaps. And there is no way for corrosion to get ‘underneath’ this stable covalent bond. The molecular bonds form through the sharing of electron pairs
So here is the "Rust Creep" problem - from paint, etc.
Traditional barrier coatings fail because they sit like a tarp over the steel, and once the tarp is torn and moisture enters, the steel corrodes. By definition, barrier coatings always fail, because once a barrier coating is compromised corrosion spreads like a cancer.between the atoms in EonCoat and the atoms in the steel.
The ceramic functions as a phosphate reservoir to continuously protect the alloy. If the ceramic is scratched or chipped it has no effect on the corrosion protection of the alloy. So the steel is still protected. And even if someone cuts a scribe line through the ceramic and through the magnesium iron phosphate alloy, the ceramic layer will leech phosphate to re-alloy the steel.
fascinating.
A characteristic of phosphoric acid is that it does not eat up rust as fast as other caustic agents like hydrochloric acid. Since it works more slowly to dissolve rust and it can be left on a metal surface for a longer amount of time.
Phosphoric acid causes a chemical action through which hydrogen is formed. Hydrogen can cause hardened steel to become more brittle. This is called hydrogen embrittlement and will be discussed in detail later in this chapter. In any case, parts made of high-strength, heat-treated steel are prone to this problem and should not be cleaned for long periods of time with phosphoric acid.
OK there you go.
Keep in mind though that this coating is thin and not very durable. It should be considered temporary protection until a primer can be applied. Some hardware stores sell a diluted phosphoric acid product called Ospho that works well to remove rust on old car parts.
Acids will not work on cast iron and spring steel. If treated a long time, spring steel will vanish in days.
OK I will go put baking soda on the Shock Springs that I sprayed! oops.
http://www.secondchancegarage.com/resto-mod/resto-mod-5-1.cfm
All car manufacturers use a phosphoric bath to wash the bare steel bodies in before paint is applied. It is done immediately before the primer is applied.
https://www.mtfca.com/discus/messages/118802/124463.html?1267622114
https://rejel.com/blog/one-of-the-key-differences-between-a-rust-converter-versus-rust-remover/
Many car enthusiasts will argue that rust converters don't work because they don't prevent rust. A rust converter is not designed to rust proof but rather the inert compound formed once rust is converted forms a barrier layer to corrosion. For any ageing car, regularly applying rust proofing will protect from corrosion. There may, however be vulnerable areas to the wheel wells, undercarriage, area around the windscreen or bumper where rust could appear. These medium areas of iron oxide formation are where rust converters are best indicated.
How effective is a rust converter? Very effective if you choose a rust converter that penetrates deep into the rust and you prepare the metal surface as per the product guidelines.
This inert layer then acts as a barrier layer or protective coating.
A rust converter eliminates the need to sandblast rust therefore less time and energy is involved in the process. These products can be used for a wide range of applications: vehicles, trailers, industrial equipment and machinery, farming equipment and domestic outdoor fittings and fixtures.
Prior to application remove flacking rust with a wire brush (rather than sealing it in), clean and degrease the area so that any contaminants present don't interfere with the conversion of iron oxide.
Applied to the undercarriage of a vehicle, it is good practise to then follow this process with applying an underbody wax for long-term rust prevention.
The key benefit of Dinitrol RC 900 rust converter is that it penetrates rust 7 to 10 times deeper than standard rust converters.
Dinitrol RC800 rust converter does not contain lead or phosphoric acid
https://before-n-after.co.uk/rust-converter.html
why not to use dinitrol
2 H3PO4 + Fe2O3 → 2 FePO4 + 3 H2O "
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