RABBIT TRAILS: Dealing With Rust, the Old School Way

[Dejure]

269K views · 9.4K reactions | $3 Liquid KILLS ALL Rust. PERMANENTLY. No Mechanic. No Shop. BIG AUTO BURIED THIS. | America Just

$3 Liquid KILLS ALL Rust. PERMANENTLY. No Mechanic. No Shop. BIG AUTO BURIED THIS.

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AI Overview


Tannin baths, commonly using tannic acid, interact with iron and steel to form a protective, blue-black ferric tannate layer that converts active rust into a stable, corrosion-resistant surface. This process, acting as a natural chelating agent, adheres well, improves corrosion resistance, and is used for conservation and surface modification.
Key Effects of Tannin Baths on Metal:

• Corrosion Inhibition/Passivation: Tannins act as inhibitors, especially on steel and iron, by forming insoluble iron-tannate complexes that deposit onto the metal surface, forming a protective, dense film.
• Rust Conversion: On rusted iron objects, tannic acid reacts with iron ions to turn rust into a black-blue, stable protective layer, halting further corrosion.
• Surface Modification: Tannin treatment turns iron surfaces dark blue, gray, or black, which is highly desirable in art and textile applications (e.g., printing and dying).
• Corrosion Rate Regulation: While tannins reduce corrosion by forming a protective layer, the effectiveness depends heavily on the concentration and the pH of the bath, with lower pH often required to enhance passivation in certain environments.
• Metal Affinity: Tannic acid has a high affinity to chelate with metals, particularly iron, but can also work with aluminum alloys and other transition metals.
  

Common Application:

• Surface Preparation: Before treatment, iron objects should be cleaned of dirt and grease.
• Concentration: A typical tannic acid solution used for treating iron objects is around 2% to 10% weight/volume, often applied in water.

Disclaimer: Tannin treatments are often used to stabilize rust, but extreme concentrations or high pH can alter the coating's effectiveness.

 

[bucket]

I didn't watch the video, the title told me enough that I don't need it in my watch history. But your description sounds like the very stuff that has been available from oodles of companies for a very long time. Converts rust to a black/blue, kinda transparent, primed surface. "Big auto" didn't "bury it".

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[bucket]

Also, while it is a product that is very useful in some instances, it most certainly does not stop rust permanently.

 

[Frankenchevy]

Phosphoric acid is relatively cheap. $18 for a gallon.

Klean-Strip 1 Gal. Concrete Etch, Metal Prep and Rust Inhibitor Outdoor Cleaner GKPA30220 - The Home Depot

Remove rust from iron and steel surfaces with this Klean-Strip Phosphoric Prep and Etch. Features galvanized and aluminum finish.

www.homedepot.com

 

[Dejure]

Bucket, yep. A lot of us were looking at ways to treat rust decades longer than a lot of members have been alive, so are well aware there are commercial products. In fact, we used to buy our rust treatment by the gallon (not just phosphoric acid) to treat our farm equipment each fall.

The ENTIRE purpose of this post was to offer information for those who want to do more than just click a mouse or shop an auto parts store. That is, it is for those who want to know what it is that's doing the job that needs to get done.

Aside the fact many products don't come cheap, this is a good start point for learning about rust treatment. Diving in a bit, it becomes obvious many of those fancy packages are just combinations of, for example, tannic acid and phosphoric acid, for the best both have to offer, since both have advantages over the other.

Consider the comment about how cheap phosphoric acid is. That is true, BUT it does not react with the rust the same way, which is why many companies use it with the tannic acid.

And, yes, there are no magic bullets. However, in this case, we can reduce how much work we have to dedicate to combating rust. Such as by sealing the metal after it's been treated.

 

[Dejure]

ANOTHER thing to look into is, a product found in paint sections at hardware stores, Penetrol.

Penetrol is an additive for oil based paints (Flotrol is the latex-waterborne version, and of no value to us for these purposes).

A few decades back, when I was researching protecting hard to reach places on my rigs, research showed a lot of car restorers used Penetrol, to treat, for example, the insides of car doors.

It's worth looking into, but treating with the tannic acid and phosphoric acid mix first, then following up with Penetrol (surface coat over the protective layer) might offer some impressive protection against rust issues.

 

[Dejure]

In addition to the above, I have used and keep in my shop Corrosion X. There are two versions. One hardens and the other remains sticky. Both perform amazingly. In fact, I've used it on my machined tablesaw top. Normally, setting a pop can on it would leave rust in just a few minutes. Treated with Corrosion X, it came out unscathed.

CorrosionX

CorrosionX products feature a unique Polar Bonding™ technology that causes it to stick to metal like a magnet – displacing moisture, preventing rust a corrosion, and lubricating metal wear surfaces.

www.amazon.com

 

[Dejure]

Franken... Yep, it works, but works differently than the tannic acid. Searches indicate a better solution is, combining it with the tannic acid, which is why commercial versions of rust treatments do.

 

[sealacamp]

Ospho works very well. I used in my restoration. Active ingredient more concentrated than others, phosphoric acid. Leaves a zinc phosphate coating behind mitigating future rust. Rust blaster, KBS coatings, and metal ready, POR 15 products use the same ingredients but not as concentrated. Tannin might work too but the acid is not as strong and probably won't affect heavier areas as well as the phosphoric acid does. I had a ton of rust to deal with, been over a year since the last repair areas were finished, so far so good. We'll see how it holds up.

 

[Ricko1966]

I didn't watch the video, the title told me enough that I don't need it in my watch history. But your description sounds like the very stuff that has been available from oodles of companies for a very long time. Converts rust to a black/blue, kinda transparent, primed surface. "Big auto" didn't "bury it".

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His video was about tanning acid most of the common stuff is phosphoric acid. Tanning acid is the active ingredient in Rustoleum rusty metal primer and a couple other products I can't remember. But most products and commercial applications,auto manufacturers,ship builders,bridge builders use phosphoric acid. Yea this stuff wasn't buried and it's actually used.

 

[Dejure]

Sealacamp, that might be the one which came out on top in tests Project Farm did (it started with an "O"). Second was an Eastwood product.

NOPE, I wasn't close. It was POR-15, at about $30.00/bottle, but highly rated.

 

[Dejure]

One site claimed things like lacquer were all but a waste of time, for protecting metal from rust. From my decades of dabbling with [primarily wood] finishes, surface coats like lacquer are far from permeable, for purposes of dealing with water intrusion. To the contrary, they add a good layer of protection.

The difference between, for example, latex versus oil based finishes, can be seen by, if both those finishes were made to contain a little water, the latex would appear to sweat, as the water (the world's greatest solvent) worked its way through, while the oil based would not show the same results. So too it would go for lacquer vs lesser finishes.

I haven't got to that road yet, but my money is on that many of these treatments would be far more durable if protected by a layer of non permeable paint.

 

[Dejure]

An important thing to note about many of these protective finishes is, they rely on, that is, REQUIRE, rust to work. Accordingly, cleaning the project down to bare metal negates the effectiveness of products that convert rust.

Tannic acid reacts, chemically, with rust (iron oxide) to transform it into a stable, blue-black ferric tannate layer.

Phosphoric acid removes rust by, chemically, converting it to stable iron phosphate. It, also, etches bare metal, improving paint adhesion.

Many products use tannic and phosphoric acid simultaneously because the two work synergistically, producing a more durable, protective coating on rusted metal.