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Average life expectancy of just metal

I want to know the average life expectancy of just metal for a piece of work I'm doing.

Cameron P.
school - Hertfordshire, Stevenage, England
April 18, 2009

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Hi, Cameron. It's a surprising coincidence, but the average "life" of just metal is very close to the life expectancy of just an animal or just a plant.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 20, 2009

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Cool :-)

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
April 23, 2009

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Hi, Sheldon. I'm really not trying to waste the kid's time or be satirical. Every once in a long while, a kid understands a point made this way and tells us s/he has a better appreciation of their project.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
April 24, 2009

I thought that it was a really deep answer. Every time I read it I got a slightly different take on it. Jim

James Watts
- Navarre, Florida
April 24, 2009

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Cameron,
It depends on which metal or alloy is being used, the treatments or coatings that have been applied to it, the environment it's being exposed to, and the physical stresses it's subjected to. It also depends on what exactly is considered a "failure" of the piece.

Ray Kremer
Stellar Solutions, Inc.

McHenry, Illinois

April 29, 2009

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May 22, 2009

Cameron, the average life expectancy for a piece of metal is almost an unanswerable question. It all depends on what metal is being used. For instance, gold, which is a metal, is very unreactive an doesn't corrode, so it can happily be in existence for many thousands of years - just think of the ancient Egyptians and their artifacts.

On the other hand, back in the 1960s it was the policy of some car makers to build cars that rusted away in four or five years. This was in an attempt to boost their sales. Unfortunately, the Japanese car manufacturers realised this was not what the car buying public wanted and designed cars to last much longer - hence the collapse of the western world's car industry!

The answer to your question should be "How long do you want it to last?" because you can decide what metal to use after you have decided how long you need the article to last.

As a general guide, the shortest lived metal objects are made from iron, followed by aluminium, then copper silver and gold. Iron will rust very quickly, especially in the UK, whilst aluminium, which is a much more reactive metal, produces its own protective coat of oxide on its surface.
There are many ways to extend the life of metal objects, including making them thicker, so there is more metal to corrode away before it becomes useless, or you can coat the metal with another, less reactive, metal, or paint the metal with a conventional paint or with a plastic coating.

There is a whole science around this subject - it is called corrosion studies and involves a combination of chemistry, physics, biology and even geography. Solving the problems of corrosion could earn you a lot of money and would be considered by many people to be environmentally friendly, as the products you make will last a long time and will not need replacing with new ones made from expensive raw materials; on the other hand some people consider corrosion protection to be non-environmentally friendly because it stops things rotting down!
You can look at everything from at least two points of view and this is where lots of science gets fun!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK