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Science project: Iron Nail in Bleach

Hello,

I am a grade 12 student in "university" chemistry. I too have final semester projects in my class. This year I was assigned Corrosion. My task is to provide a 15 minute lesson for my peers, teaching them about the causes of corrosion as well as ways to prevent corrosion. My question is this: I know what corrosion is and how to prevent it, but to make this project interesting I decided to add an experiment. I was wondering if you would be able to explain to me in words that an average student can understand, what it is that is in bleach that causes an iron nail to corrode so drastically. I think it has something to do with hypochloric acid, but I am not 100% sure. Any advice you can give me is much appreciated, and if you can't help me directly I would really appreciate direction to a web site that may assist me. Thank you so much in advance.

Chris N. [last name deleted for privacy by Editor]
student - Mooretown, Ontario, Canada
2004

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2004

As a side note I think it's called hypochlorous acid rather than hypochloric, but don't even THINK about adding acid to bleach because it will release poisonous chlorine gas.

Bleach is sodium hypochlorite (NaOCl). To stabilize it, i.e., to retard it from vaporizing as chlorine gas, it contains a lot of caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] (NaOH). Caustic does not corrode steel, so it must be the NaOCl. Look at the oxidation states of the atoms in the sodium hypochlorite and note something rather unusual. Is the oxygen in the common -2 state or is it in some other state? If the -2 state is far more common, which state do you think is more stable? If the -2 state is more stable, the oxygen 'wants' to move to that state. If the oxidation state of the oxygen must be reduced dramatically to get there, what must happen to the oxidation state of some other atoms? Combine the effects of water, chloride, and a powerful oxidizing agent, and you have a very strong rust-inducing medium.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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Hi! I am a 5th grade student, 10 yrs. old, and I need help on my science project. I've never done one before. My project is "Which clean nail will rust faster in different substances?" I already have my substances (Coca-cola, bleach, Water, tap water, coffee, and Diet 7up.) On my background info, I need to find out what rust means. I've looked in my nearest dictionary, but haven't been able to find the word rust. I also want to know who first found rust. I've practically looked at every site for that, but yet, still haven't been able to find anything. I desperately need help from you, Ted Mooney! I've looked at lots of comments on here, but they're normally all above my grade level. Please answer soon! Thank you, :)

-Alexis R.

Alexis R. [last name deleted for privacy by Editor]
Student - Chesterfield, Missouri U.S.A
October 14, 2010

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October 14, 2010

Hi, Alexis. You may have heard of the Stone Age, the Bronze Age, and the Iron Age. Mankind started with tools made only of stone, bone, and wood. Later we figured out how to make bronze tools. Later still we found out how to dig up iron ore, and heat it very hot in the presence of coal or a similar material that sucked up all the available air from the iron ore and make metals like iron and steel from it. Steel is made from the same stuff as iron; it's just very pure iron with very small amounts of contaminants added to it to make it a more versatile metal.

Much much later we learned to invent a written language and start recording history.

The iron or steel that we make is a wonderful, strong, versatile, and inexpensive material from which we build cars, trucks, trains, bridges, towers, screws and nails, and many other things. But one disadvantage it has it that, over time, the iron or steel reacts with the oxygen in the air and converts to rust. Rust is orange-brown powdery stuff and has no strength at all. Your parents may be able to find a rusty nail or other rusty steel object in your garage or basement to show you. A little bit of rust is not a problem except for being ugly and maybe staining your clothes, but after a long enough time, as there is more and more rust, and less steel left, the object isn't strong enough to do its job anymore and the bridge would break or the tower would collapse

I mentioned that we didn't invent written language until long after we invented iron, so we will never know who first found rust.

Your experiment will involve putting nails into bowls of your chosen liquids and trying to determine which ones cause the nail to rust fastest. You'll probably look at the nails once a day for a week or so, and see what you see, keep some notes, and write a short report about it.

If at all possible, try to get to a library. Librarians are good at helping you find information: that is their job. And books are a better and more reliable source of information than web sites.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey