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topic 9887

Rust Conversion- Can you help?


Q. Hello,

I have applied Neutra Rust 661 on a fairly rusted piece of metal. The conversion seemed fine and went through described stages and the result was a black layer. Two days later I attempted to scratch this black layer and was surprised to see the brown/orange'ish color beneath the black layer! My understanding is rust should have been totally converted to a black compound. Much appreciated your explanation.


Ross Rostane
- London, UK

"Phosphating & Metal Pretreatment"
by Freeman

from Abe Books
info on Amazon


A. I would start with a bright iron or steel surface first. I would not expect the chemical to remove the rust completely, then to deposit a black layer. It probably did as best as it could with some complexing and reducing agents.

pooky tom pullizi signature
Tom Pullizzi
Falls Township, Pennsylvania

A. It sounds as if rust layer was pretty thick and some of it needed to be brushed off. The surface needs to be cleaned of excess rust. That means removing rust flakes and dust but do not remove all the rust or no conversion will occur. A rust converter is a product that reacts with the iron oxide, converting it to iron tannate, a stable blue/black corrosion product. If the rust layer is too thick it may not convert all of it.

Juanita Mercure
- Houston, Texas, USA

"Phosphating of Metals"
by Werner Rausch

from Abe Books
info on Amazon


A. Perhaps this as you know was counterfeit product purchased from corrosion control formerly known as Neutra rust Inc before I found out that they were selling a counterfeit product. If you want the real Neutra then feel free to contact me at Neutra rust international.

Beverley Hancock
- London, England

Ed. note: There are countless brands of rust converters, including simple Naval Jelly [linked by editor to product info at Amazon]. Now that this thread has descended from a technical discussion of rust conversion to something akin to siblings whining about who is on whose side of the back seat, perhaps the readers are learning for themselves why we ask them to please keep the discussions generic, focusing on chemical reactions & mechanisms, and avoid mention of brand names :-)


Q. I have used Neutra rust many times and have been especially impressed with its function and amazing durability on my snow plow blades and cutting edges! What product(s) would you recommend for refinishing rusted automotive exhaust manifolds with a minimum of rust removal? I am more interested in protecting the metal than appearance.

Joe Tutela
corvette restorer - Flanders, New Jersey

A. Hi. First choice would be ceramic coating, second choice would probably be high temperature paint. As for rust converters, there are a hundred brands and it's okay for people to write advertisements claiming "my secret formula is better than the other 99 secret formulas, says me" . . . but such ads & testimonials don't belong is this forum of camaraderie and technical information exchange :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

December 25, 2012

Q. Where can I buy rust converter in Australia? Thanks.

Floyd Treasure
easy turn - Australia

Ospho Rust Converter

October 23, 2015 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I wanted to convert rust and heard phosphoric acid converts red rust into more harmless black rust.
I dipped my steel into "prep and etch" which has 30-40 percent phosphoric acid and other secret substances.
Even after long exposures (3h+) the red rust stayed red but appeared more loose. Blank shiny metal parts of my steel however turned black.
What could that be? Black Iron Oxide or Iron phosphate or something completely different? Thank you.

Jens Schuetz
- El Dorado Hills, California, USA

October 2015

A. Hi Jens. A problem with red rust is that it's not adherent; it was already non-adherent before you started, and conversion won't make it adherent. I believe you should use a wire brush to remove as much red rust as practical before doing rust conversion, and then expect a grey color to develop. The grey color is iron phosphate.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

October 26, 2015

A. I've heard of hypophosphorous acid being used for this.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

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