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Science Project: Copper Rusting


I am a 6th grader doing a science project which asked the question, how long does it take for copper to rust in the following environments: a. Ice cold water b. Damp dirt c. Hot salt water. I have pieces of copper pipe in jars with these three environments & am waiting for the pipe to rust. I am also doing research on the web. Would you please help me answer this question.

Thank you,

Jessica D
- Brooklyn, New York, USA


Strictly speaking, Jessica, copper won't ever rust since the word 'rust' is reserved for the corrosion products of iron, not the corrosion products of copper.

I suspect you're going to get quite tired of keeping ice in the ice water long before your copper pipe rusts in ice water. The pipes feeding the plumbing fixtures in your home are probably copper and have probably been full of cold water for many years. Copper plated grounding rods have a life span of decades in damp dirt. So I'm betting on the hot salt water as the only thing having even the slightest chance of corroding copper by January 24th.

Ted Mooney   Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


Hello Jessica!

One of the places you want to check out on the web is the site for the Copper Development Association. Just type that name into your favorite search engine, and you'll likely get there. They have a nice section on copper pipe, as used for plumbing applications, and even have a few paragraphs about corrosion resistance.

Good luck, and have fun!

Lee Gearhart
East Aurora, New York


In this country, copper doesn't rust. It probably doesn't in your country, either.

Bill Reynolds
   consultant metallurgist
Ballarat, Victoria, Australia

It is this website's profoundly sad
duty to relate the news that Bill
passed away on Jan. 29, 2010.


Perhaps Mogan's teacher misspoke and meant oxidize, instead of rust. She may be looking for the amount of time it took for copper to develop that green patina.

Marc Green
anodizer - Boise, Idaho


Thanks, Bill. Thanks, Mark. I'm not concerned that Jessica's teacher inadvertently called the corrosion products of copper 'rust'. That's an easy mistake and maybe unimportant depending on the grade level.

What bothered me was we always encourage the students to actually *DO* the experiments and Jessica was asked to keep a piece of copper pipe in ice water until it rusts. Anyone wanna volunteer to do that one for her? Not me--I think it will take bailing and fresh ice cubes every night for many years years :-)

Ted Mooney,   Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


I am a 6th grader doing a science project and I need to find out if some pennies and some nickels rust faster in salt water, bottled room temperature water, or faucet water. Please answer this question.
Anthony R

Anthony R
student - Sachse,Texas


Please don't ask us or anyone else which water the coins will rust fastest in until you have done the experiment, Anthony. Trying to make an experiment come out "right" is called "junk science" and is a terrible plague. The way to counter it, especially when you don't yet have years of experience in it, is to make sure you don't look for other people's results until you own have been carefully documented in your "lab book". Good luck.

Ted Mooney,   Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


Hi everyone, I'm a 6th grader! Does copper rust or not? Please give me a straight answer and explain a little. Please do not use pipes or what not. THANK YOU SO MUCH!

Irena T
student - Singapore

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We have said above that copper can corrode but it cannot "rust", Irena, because the word "rust" is reserved to mean the corrosion products from iron corroding, and copper is not iron.

Since you are not understanding that, let me repeat an answer I've given on several other threads (I apologize to those who have looked at a lot of threads and are bored with it).

An old cabbage can rot and an old fish can rot, but an old fish can never become a rotting vegetable because the word "vegetable" is reserved for certain kinds of things and a fish is not one of those things. In exactly the same way, copper can corrode or tarnish but it can never rust because the word is reserved for a certain kinds of thing and copper and its corrosion products is not that thing.

Ted Mooney,   Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey

March 27, 2008

Please explain why some copper pieces that I have acquired look like they have rust. Are they combo iron copper metal (alloys, perhaps)? These are things like planters, bird feeders, etc., which have been exposed to the elements. Most of them are castaways that I find interesting. How do you suggest that I restore these pieces, if possible? Thanks for your expertise and consideration.

B. Hammond
- Houston area, Texas

March 27, 2008

Hi, B.

Steel electroplated with copper is less expensive than solid copper sheets, so a lot of what people think is "copper sheet" is actually copper plated steel sheet, and that is probably what you have. The underlying steel has apparently rusted. You may be able to remove some of the rust with a metal polish (lightly applied so you do not remove the copper plating). But once it has begun to rust because of pores in the copper plating, it will continue to rust unless you wax it and keep it indoors, or spray it with a clear coat. Good luck


Ted Mooney,   Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey
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