Letter 27023

Effect of Temperature on Corrosion [California] 

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Hi! I'm a high school student attending California Academy of Mathematics and Science. I'm preparing a sciece fair topic about corrosion. I am planning on doing it about the effects of different temperature on the corrosions of metals. The metals that I will be using are copper, tin, brass, stainless steel, aluminum, iron, galvanized metal,and zinc. I will have three different settings; room temperature, freezing temperature(put metals on frezer) and warm or hot temperature. The problem is that I dont't know how to keep the warm/hot temperature constant. Do you have any sugestions? I also wanted to know what chemical I should use to speed up the corrosion? Which one acts faster? Any help would be greatly appreciated.

Cesar R.
student - Huntington Park, California, United States

An interesting project, Cesar, but you'll have some major issues. It's not just that you'd need a way of keeping the temperature constant, but as soon as you apply a chemical to speed up the corrosion you have corrupted your premise, and all you will have left to report on is the effect of that particular chemical on that particular metal at that particular temperature.

As an example, suppose we tell you that salt will speed up the corrosion; now with salt the stainless steel may corrode quickly, whereas without the salt it might have lasted millenia. If we suggest a mild mineral acid, that will dissolve the zinc in an instant while having almost no effect on the copper; nitric acid will wreak havoc on most of the metals without bothering aluminum; caustic will quickly dissolve aluminum but not bother stainless steel, etc.

Another problem is that galvanized metal is steel that has been coated with zinc; it's not really comparable to the other metals which are 'solid'. Once you get down to the steel, you have a different situation.

The purpose of the study of science is to help us understand the world we live in, so I'd try for something broad and vaguely related to a real life situation. Like maybe what is the effect of splashing sea water on these materials at subfreezing (your freezer), cool temperatures (your refrigerator), relatively constant temperature (indoor room temperature) and varying outdoor temperature. So I'd say mist them with salt water a couple of times a day. I think you'll find that if you can leave them in the sun so they wet and dry, that you will find the quickest corrosion. But that's a guess, and one experiment is better than a thousand guesses.

 
Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

Ted,

I recall, a couple of months ago, a girl had asked for help on a similar problem where she was trying to see the effect of soil on steel shovel at different temperatures [Letter 24686]. I wonder if that discussion could be of help to Cesar here.

Mandar Sunthankar
IonEdge Corp. - Ft. Collins, CO

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Thank you for answering my previous question so fast. After reading other questions and doing research I decided to change my topic. I want to know what is the effect of different voltage on the amount of anode deposit on the cathode. I am thinking of using either aluminum or copper as the anode and stainless steel or brass as the cathode. Which should I use? What should my bath be made of in order to dissolve the anode? I also wanted to know what voltage's should I test and which battery or source should I use? Can I combine batteries? Any help would be greatly appreciated.

Cesar Ramos
Student - Huntington Park, California, United States

The amount of deposit on the caathode is directly proprtional to the current times how long you plate for (ampere-hours) according to Farday's Law. The current is 'sort of' proportional to the voltage in accord with Ohm's Law. The 'sort of' proviso is because of some fixed losses in the system.

Aluminum is not electroplateable, so don't use that as the anode. Use a copper anode. Depending on what grade you are in, and how watchful the eyes that will keep your classmates out of the experiment, different acids are appropriate. Sulfuric acid is a good choice if you're in a high school lab.

Ted Mooney, P.E.
finishing.com Inc. - Brick, NJ

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