Rust as protective coating on bridge steel?

[fried1765]

The electric co-op in our area put something like that on some major transmission poles. Must have been some form of experiment. It was only done on a dozen or so. Turned them from big galvanized structures to a chocolate brown color - more or less. Guess it didn't pass the "sniff test" - they never did any more of the poles.

Out going across the wheat country chocolate brown blends in no better than galvanized.

"Corten" steel is often used for tower and bridge structures. The surface rust that forms, is intended to provide a weather protection.

 

[Mat4644]

On bridges any place on the steel that collected any type of debris that retained even a small amount of moisture there would be continued rusting and eventual rust through.

 

[ArlyA]

"Corten" steel is often used for tower and bridge structures. The surface rust that forms, is intended to provide a weather protection.

You got it, the steel alloy is Corten. Its been around for many years and it works as designed. I welded it when I work in the RR industry as a carmen in 1980's. We asked for the price of using corten for a bridge we needed a few years back and that added about 3K to the project. We didn't go with it.

 

[skipmarcy]

They've been doing bluing on firearms for many, many years. You rust the metal chemically then card it, then one coat of oil and it will last many years. Depending on which chemicals you use to "rust" the metal will determine what color your bluing will be.

 

[tallyho8]

A bridge not far from home is made with rust protective steel.



The Hale Boggs's design features an unpainted weathering steel towers and superstructure, an orthotropic steel box girder superstructure, and two planes of cables in a fan pattern. Weathering steel exhibits uniform oxidation or "rusting" that results in a uniform protective patina and reduces maintenance requirements. The bridge's weathered bronze color is intended to blend with the muddy waters of the Mississippi River. "Wiki"

 

[jonathanstarr]

I used to own a company that made a lot of large steel structures for signage. Airport projects in particular often called for corten steel for the structures. This would rust on the surface in a few months, and then the rust would advance very slowly of the course of it's life. The design had to work within the strength and attribute parameters of the steel. Mayari steels, such as ASTM A242 have similar properties. Architects hated the stuff, because the surface rust would run off onto whatever was below the steel, and streak concrete or roadway surfaces with rust.

 

[tookielee]

I've had a few cars that developed that coating!

 

[2LaneCruzer]

I've had a few cars that developed that coating!

The car guys I know call that a "Patina".

 

[Lineman North Florida]

Out here in the land of fruits and nuts our local power company is starting to replace wooden poles with steel. The portion that is buried is coated in a black tar looking substance but the rest is bare steel that is rust covered. When they first started this I read an article that said they were coated with some kind of chemical that caused the rust covering and that it acted as a preservative. It looks like a good idea but I wish they would hurry up and get it done as we are looking at a potentially bad fire season right now.

They are ductile iron poles, we have been using them for a number of years, they are much lighter than concrete and don't require a crane to set them, we have had good luck with them.

 

[grsthegreat]

The power companies here are installing steel sectional power poles inplace of wooden ones for standard transmission poles. So many wooden ones kerp snapping when trees come down, its hoped this stops that. Now all they need to do is repair wires, not remove and reset poles. One windstorm a few years back took out 3,500 poles. These poles are weathering steel coating. Look kind of nasty, but hopefully they will make for shorter outages.