How to Fight Rust With Chemistry

Tim
By Tim Suddard
Jun 6, 2021 | rust, Shop Work | Posted in Shop Work | From the Aug. 2014 issue | Never miss an article

Photography Credit: David S. Wallens

[Editor's Note: This article originally appeared in the August 2014 issue of Grassroots Motorsports.]

Chemistry enhances our lives every day. It causes light bulbs to illuminate, OxiClean to whiten our whites, and Doritos to be delicious. It can also be used to fight rust, a popular adversary. 

Evapo-Rust

What Is It?
It’s a watery liquid that chemically sucks rust off rusty parts. 

How Do You Use It?
We usually just soak the offending part in a bath of Evapo-Rust, but you can also apply it to a rag and use it like a cold compress. Evapo-Rust can be reused, too. In fact, they say that one gallon of Evapo-Rust can treat up to 300 pounds of steel. (When the liquid has turned black, then it’s no longer magical.)

Does It Work as Advertised?
We’re pretty sure there’s some black magic involved, but this stuff really does make rust disappear. What do you do with the liquid afterward? Its maker recently shared this tip with us: Put it into a garden sprayer and spray it on your lawn. Your grass will appreciate the extra dose of iron. 

Evapo-Rust
evapo-rust.com

POR-15

Photography Credit: Tim Suddard

What Is It?
It’s a thick, paintlike liquid that, according to its manufacturer, bonds to rusty metal. 

How Do You Use It?
It’s usually brushed on, although it can be thinned and shot from a gun. Your color choices are black, silver and clear. If it’s being applied to a surface that gets a lot of sun, plan on topping the POR-15 with paint. 

Does It Work as Advertised?
Definitely. POR-15 has been a GRM shop staple for years. Once dry, it covers the metal in a thick, smooth coating–almost like a chocolate shell, although this one won’t melt. Once POR-15 is on something, though, it’s permanent–so plan accordingly.

POR-15
por15.com

Eastwood Patina Preserver

What Is It?
This one doesn’t fight rust as much as preserve it. Think of it as a non-permanent coating that prevents the elements from making current rust any worse.

How Do You Use It?
Just spray away. Its maker recommends two or three light coats. One can should cover 12 to 16 square feet. 

Does It Work as Advertised?
This one is so new that we haven’t even tried it yet. We are fans of Eastwood’s other rust-fighting products, though, like their Rust Encapsulator Paint and Rust Converter. 

Eastwood
eastwood.com

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Comments
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1988RedT2
1988RedT2 MegaDork
5/17/21 12:40 p.m.

I've used both Evapo-Rust and POR-15 quite a few times over the years.  My only beef with Evapo-Rust is that it takes a long time.  Figure at least 12 hours submerged for anything that could be considered even a little "rusty."  Even longer if it's quite rusty and pitted.  Still impressive, in that you don't have to be grinding it, or blasting it or sanding it.  Just "kerplunk" and forget it for a while as the Evapo-Rust does its thing.

GIRTHQUAKE
GIRTHQUAKE Dork
5/17/21 12:49 p.m.

Evapo-rust works via a process called "Chelation", where a mix of chemicals pulls a metal element out of an ionic bond, only here to then be replaced by another element that then drops said chemical out of the compound. What's exactly in it is obviously a trade secret, but the black is raw iron in suspension.

To this, I'd like to add Geoff Croker's video on rust treatment which I think should be made into a wall tapestry and put somewhere in view of any shop that uses metal. The goofy voice he sometimes takes is grating, but he shows what genuinely works best- my "rust treatments" have now almost entirely been pared down to several electrolysis baths, citric and oxalytic acids, and some samples of evapo-rust for things I cannot afford to have pitted.

 

SteveMeyer
SteveMeyer New Reader
5/17/21 1:17 p.m.

no mention of electrolysis?

or was this simply advertorial. 

David S. Wallens
David S. Wallens Editorial Director
5/17/21 1:48 p.m.

In reply to 1988RedT2 :

I don't mind the wait on Evapo-rust. I have used it on bike and guitar parts, too. Set it and forget it. I think I dunked everything in a plastic container fished out of our recycling bin. smiley

1988RedT2
1988RedT2 MegaDork
5/17/21 2:00 p.m.

In reply to David S. Wallens :

Yup.  Recycle bin is my go-to for suitable containers.  Works great for small items.  Big stuff is more of a challenge.

David S. Wallens
David S. Wallens Editorial Director
5/17/21 2:27 p.m.
1988RedT2 said:

In reply to David S. Wallens :

Yup.  Recycle bin is my go-to for suitable containers.  Works great for small items.  Big stuff is more of a challenge.

Reduce, reuse, recycle. 

Scott Skillman
Scott Skillman New Reader
5/17/21 4:24 p.m.

For years, I have used Ospho, it is cheap and effective. It is surprising that Ospho was not listed here since it has been around for decades.

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.

 

1988RedT2
1988RedT2 MegaDork
5/17/21 7:01 p.m.

In reply to Scott Skillman :

Is Ospho the same as the so-called Rust Converter sold under a variety of brands?  Sounds similar.

 

nash300z
nash300z GRM+ Member
5/17/21 7:46 p.m.

POR 15 is wild stuff.  Wildly toxic, but also wildly effective.  

 

I love how you brush it on like third-grade art class and it dries like shiny powdercoating.

 

pirate
pirate HalfDork
5/17/21 8:03 p.m.

I'm surprised someone hasn't said "don't get it on your hootus" yet.

Mr_Asa
Mr_Asa UberDork
5/18/21 2:19 p.m.

POR-15 is decent stuff, but I waffle on whether I'd put it in the rust fighting category.  It prevents rust, sure.  However, if I remember my chemistry, if you just slap it on over rust it doesn't do anything to actually convert the rust.  It'll hit the top layer and stabilize that, but that's all.  

 

As a tangent, I wish there were something that I could use like Evapo-Rust for aluminum.  

aircooled
aircooled MegaDork
5/18/21 4:47 p.m.
Mr_Asa said:

....As a tangent, I wish there were something that I could use like Evapo-Rust for aluminum.  

Oven cleaner?

oneway
oneway New Reader
5/19/21 7:51 a.m.

EVAP-O-RUST has been an amazing component in my resurrection project of  a 78 280Z.  The best part besides that it works so well is the dunk it and not worry about it time slot.  My work schedule and life priorities often interrupt the resurrection project and sometimes it may be several days later before  I get back to that rusty component.  After washing the parts I have been using a rust converter spray from TP TOOLS and then priming with KRYLON  Rust Tough Primer then top coating with an appropriate color choice. The parts look great.  Just wish I could squeeze the while car into the EVAP-O-RUST jug.  I have also been using the TP TOOLS RUST COVER PAINT on the large areas-floor pans, valances, headlight buckets, etc and have been very pleased with the results so far. Thanks for the great info, John-Lugoff, SC.

stuart in mn
stuart in mn MegaDork
5/19/21 7:59 a.m.
aircooled said:
Mr_Asa said:

....As a tangent, I wish there were something that I could use like Evapo-Rust for aluminum.  

Oven cleaner?

Never use oven cleaner on aluminum, it will damage it.  NAPA sells a product in a spray bottle called aluminum brightener that works pretty well.

Tony Sestito
Tony Sestito PowerDork
5/19/21 8:10 a.m.

Totally sold on Evapo-Rust. Used it for the first time recently on some crusty fuel line clips from my Trans Am.



I didn't know there were any markings on these!

Also tried it on a crusty fuel sender for my truck.

Before:


After:


Not as drastic, but it cleaned up a lot. It also exposed some pin holes I couldn't see before that I need to seal up.

Also tossed a set of pruning shears I found in the dirt outside that were rusted solid. They came out looking brand new! And the best part is you can reuse the stuff until it's not effective. Great for small stuff.

300zxfreak
300zxfreak Reader
5/19/21 8:54 a.m.

I can't believe that no one has mentioned the cheapest rust remover going, apple cider vinegar. I have used it, full strength, to clean parts, inside motorcycle gas tanks, old tools, etc. You can re-use it several times before it becomes too weak to effectively remove rust. It's biodegradable, and makes great salad dressing mixed with used motor oil.........that last part may or may not be true, I haven't tried it....yet.

P.S.  Regular old white vinegar, to the best of my knowledge, does not work.

Tony Sestito
Tony Sestito PowerDork
5/19/21 1:20 p.m.

In reply to 300zxfreak :

I tried that on a heavily rusted small engine tank. Dumped some bolts in there, shook it around a few times, and let it sit for a while. It worked pretty well!

Mr_Asa
Mr_Asa UberDork
5/19/21 1:41 p.m.
aircooled said:
Mr_Asa said:

....As a tangent, I wish there were something that I could use like Evapo-Rust for aluminum.  

Oven cleaner?

I'll use oven cleaner only if something is so greasy that I can scrape it off with a screw driver.  Other than that it will eat aluminum if you let it sit on there.

But that's not quite what I meant.  I'm looking more for something as gentle (or almost as gentle) as Evapo-Rust is on iron.

Mr_Asa
Mr_Asa UberDork
5/19/21 1:45 p.m.
300zxfreak said:

P.S.  Regular old white vinegar, to the best of my knowledge, does not work.

There's no real chemical difference between white vinegar and apple cider.  Both are acetic acid at about 5% strength

300zxfreak
300zxfreak Reader
5/19/21 3:42 p.m.

In reply to Mr_Asa :

Not being a chemist, I can't debate what, if any, difference there may be. But, from experience I just know that regular old white vinegar just does not work as well, have no clue why, that's just the way it rolls.

tjbell
tjbell HalfDork
5/20/21 9:32 a.m.

Now what about on a frame? I just bought a cheap rusty gmt400 tahoe and the frame is pretty damn scaled in rust, no holes though. It's a rust belt car and I'm trying to find the best thing to use, so far rustoleum rust reformer looks good

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand PowerDork
6/1/21 6:39 p.m.

How about a set of long tube headers? They have to be stripped to bare steel for painting. 

GIRTHQUAKE
GIRTHQUAKE Dork
6/1/21 7:18 p.m.
300zxfreak said:

I can't believe that no one has mentioned the cheapest rust remover going, apple cider vinegar. I have used it, full strength, to clean parts, inside motorcycle gas tanks, old tools, etc. You can re-use it several times before it becomes too weak to effectively remove rust. It's biodegradable, and makes great salad dressing mixed with used motor oil.........that last part may or may not be true, I haven't tried it....yet.

P.S.  Regular old white vinegar, to the best of my knowledge, does not work.

Because it's not as cheap or as effective as powdered Citric acid dissolved in water- I got a 5lb bag of it for about $10 and a tablespoon makes a more potent acid than its equal weight in Vinegar.

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