plating, anodizing, & finishing Q&As since 1989
Why does Nickel corrode in hot, medium, and cold water?
March 27, 2012
Q. So, I'm doing a lab report on why Nickel placed in hot, medium, and cold water corrodes. The whole "scientific question" would be: How does the temperature affect the change in the metal's colour? To answer the question, I would need to know why they corrode in the first place... Which I don't. Any help? Thank you!Jennifer C
- Ottawa, Canada
A. Hi Jennifer
All metals except gold and other precious metals corrode to some extent. I'm not sure how much if any chemistry you've had yet, but the reason they corrode is that compounds like nickel oxide are more stable (have a lower energy level) than the metal has in metallic form. In a way, the metal "burns" in the air, releasing heat . . . it's just that the rate of burning is so slow as to be almost undetectable. You can only get it back to metallic form by putting energy back into it (for example, heating it with oxygen excluded). This is why it is possible to find nuggets of non-corroded gold in nature, but not nuggets of other metals like nickel. But corrosion is a very complicated issue! Not only are some metals more prone to corrosion than others, but the corrosion products of some metals, like steel, are loose and porous and fluffy, like the rust on steel; whereas the corrosion products of other metals, like nickel, are tough, tenacious, compounds that can seal the raw metal away from the environment.
The tarnish on nickel is slightly yellowish and maybe (just maybe) you'll be able to grow a thicker, yellow-er, tarnish in hot water than in cold water due to greater chemical activity. Or maybe (just maybe) because the tarnishing reaction releases heat to the environment, keeping the nickel in hotter water will slow the reaction. I hope you will be able to get enough tarnishing to find out! Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. The simpler explanation for a physical or chemical phenomena is always the best and always welcome. That was beautiful, Ted. Thank you!
Monterrey, NL, Mexico