jerryc41 Loc: Catskill Mts of NY

Years ago, they replaced the guard rails around the Ashokan Reservoir (NYC). The metal rusted almost immediately. We were told that the rust was supposed to protect the metal.

There is now a big project on the local state highway replacing the guardrails. They look fine, but they're rusty. They are being replaced with identical-looking galvanized guardrails.

Is there such as thing as metal rusts on the surface as protection? If so, why would they remove it to use galvanized, instead?

Mac Loc: Pittsburgh, Philadelphia now Hernando Co. Fl.

I’ve never of rust as protection.

DaveD65 Loc: Queen City, Ohio

Check out the New River Bridge In SW West Virginia. I read this a long time ago; this bridge is a very large span across the New River. Economically they said that painting this bridge very (10?) years would be difficult and costly. Apparently they spray on some kind of oxide on the the metal and the (rust) helps protect and reinforce the metal also. I've paddled under this bridge a few times and it almost looks like paint. Rust is sort of spotty, this looks like paint ,very smooth and even. Also since its coated the oxidization does not continue to oxidize.

Mac Loc: Pittsburgh, Philadelphia now Hernando Co. Fl.

Thanks for that info.

Longshadow Loc: Audubon, PA, United States

Only if the metal develops a patina, otherwise it will continue to rust and corrode.

neillaubenthal

There's surface rust and then there's corrosion which is more of a strength thing whereas rust is more of an appearance thing. Galvanized will also rust…it will just take a little longer.

pendennis

Originally, firearms had no rust protection, but most barrels developed a patina which provided some protection from deepening oxidation. Later gun makers used "browning" to protect the steel. Browning consisted of ordinary table salt dissolved in distilled water. There was a process used in a damp environment, and several steps were used in coating the metal, bringing it to the desired patina.

Years later, "bluing" was developed which did away with browning and provided a better protection for steel.

Here's a link to an NRA site which describes both processes: https://www.nrafamily.org/content/gun-manufacturing-browning-vs-bluing-1/

jerryc41 Loc: Catskill Mts of NY

That sounds about right. Thanks.

therwol Loc: USA

You forgot about Parkerizing, a chemical reaction between zinc phosphate and steel, typically used on military firearms.

Grump's Photos Loc: Dunedin FL

Google “ Core 10 Steel “ for info on rust as a preservative. There are a lot of states that use Core 10 Steel for highway signs and such. It only “rusts” to a predetermined depth, and will “heal” itself if scratched or nicked.
Andy

Ctrclckws

Rust is oxidation of a surface expose to oxygen.

When cut apples or potatoes turn brown, the are rusting.

Some metals oxidize on a thin layer on the surface, which then protects the rest of the material. Aluminum is like this.

Other metals rust in a way that the oxide can flake off or bubble up, exposing the underlying material to oxygen, leading to more rust, and strong destruction.
Iron and steels are like this.

Cor10 steel has additives to prevent the spread of rust. A lot of the shipping containers are made if this.

Material engineering is fun.

Schoee Loc: Europe

Weathering steel, often referred to by the genericised trademark COR-TEN steel and sometimes written without the hyphen as corten steel, is a group of steel alloys which were developed to eliminate the need for painting, and form a stable rust-like appearance after several years' exposure to weather.

U.S. Steel (USS) holds the registered trademark on the name COR-TEN.[1] The name COR-TEN refers to the two distinguishing properties of this type of steel: corrosion resistance and tensile strength.[2] Although USS sold its discrete plate business to International Steel Group (now ArcelorMittal) in 2003,[3] it still sells COR-TEN branded material in strip-mill plate and sheet forms.

BebuLamar

I don't know Jerry but I read that when I use cast iron cookware I would get some of the rust in the food and it's a good thing.

DaveC Loc: Illinois

The Chicago Picasso sculpture is made of Cor-Ten steel. So is the exterior of the Daley center. I don’t know about the Daley center but the Picasso has never, to my knowledge, been treated. It was mentioned in all of the articles about it.

BrianFlaherty Loc: Wilseyville, CA

In 1981, I closed my contracting business; and, began a 20+ year "career" as a "Forensic Expert" relative to Construction Defect Litigation. One of the first cases I worked on was a case involving the "Aloha Stadium" in Honolulu. It was designed with "movable seating" mounted on rails which were intended to allow the stadium to be be "re-configured" for different sporting events such baseball; football; etc. From Day One, it had "problems" resulting from rust and corrosion on the stadium sections and the rails on which the sections were to "travel." In fact, these sections never moved an inch. It was one of the first major uses of "Cor-Ten" steel. . .And, it was a multi-million dollar "Failure!" Literally, one of the "Biggest Jokes" in the History of stadium construction! And, almost as big as the several scams perpetrated on sports fans by the multi-traveled ownership of the Oakland Raiders . . .as the team was moved from Oakland to Los Angeles; back to Oakland; and, eventually to Las Vegas, where it currently resides (But, for how long???)

Returning to the original question re: corrosion. . .in Honolulu, the corrosion between the rails and the stadium sections "bonded" these two critical elements together. The ONLY thing that was accomplished was the staggering amount of money that was spent on attorney fees; engineering fees; and, the Public Debt passed on to the Taxpaying People of Hawaii! [I worked for one of the consulting firms for over two years; and, then, left to join another firm. The issue was never resolved. . however, I DID receive the equivalent of a post-graduate education through my close association with one of the world's foremost "experts" on Corrosion, Dr Israel Cornet! <smile>]

I hope you enjoyed that little ramble? <smile>