aluminum cans on the ocean floor

[sjo hest]

For purposes of instructing children, I need help settling an argument. I understand that an aluminum can will last a very long time on the ocean floor. A friend claims it will quickly corrode. Who is right? What's the current estimate on how long an aluminum can will take to biograde at the bottom of the ocean? Thanks, Dan

[hansp77]

My guess would be that the walls of the can would corode reasonably quickly (timewise I could only randomly guess, 1-2 yrs???) eventuating with the can breaking into two stumps, the top and bottom, being thicker would take a fair bit longer. This would fit into my experience of finding such stumpy ends...
But i really don't know.

I had to picture in what context this argument occured. By chance were you on a boat and this friend lobbed a can overboard, in front of children, before the argument occured?

[StianM]

I think they could last for a long time.

Coke is corosive too and they can keep that stuff in for years.
They are also coated with a nice logo and the deeper they go the less oxygen is there in the water so they could last longer on 2000m than on 2m.
The beer boxes I find on the beatch allways seam to look like new.

I gues someone know for shure.

[Poida]

Why is there less oxygen in the water as you go deeper?

Poida

[StianM]

Originally Posted by Poida

Why is there less oxygen in the water as you go deeper?

Poida

I asume it's because the sunshine is necesary for oxygen producing organisms and plants and sunshine don't reatch that deep. Also things that sink will nead oxygen for the proces off being rotten or oxyde.

I newer though mutch about it. I just acepted the fact it is that way without asking questions.

[jehardiman]

Originally Posted by Poida

Why is there less oxygen in the water as you go deeper?

Poida

It's colder, less aireation, and less light means less photoplankton.

I think this is a depth issue based on my experience with thin alumininum structures. In water less than 300m, they are gone fairly quickly, 5-6 months if they aren't buried by silt, even less in very shallow water where the coating is quickly abraded. If hooked in to a corrosion cell, say one steel bolt, I'd expect a can sized object to be gone in a week. Once they are buried by silt or are in deep water, we are talking decades....50-60 years. DSV-2 was down in 5K feet for a year with no appreciable corrosion in the flooded interior.

[timgoz]

At a remote Alaskan settlement the locals toss so many beer cans off the floats that if they did not degrade quickly, there would be a bloody artificial reef there. I kid you not. I was concerned when I first witnessed it. The local men fish Salmon & harvest other food from the sea. They were not concerned and assurred me cans were quickly consumed. They would dive on occassion to retrieve lost items or unfoul lines, and claimed first hand knowledge of what lay below.

I still find random littering troublesome though. My cigarette butts leave with me when I'm out, be it water or woods.

Tim

[sjo hest]

Thanks for your replies. I'd understood the cans could last a very long time, but that was at extreme ocean depths. The issue seems to be one of light and oxygen--the less of both, the longer aluminum lasts? On land the things last too long for any of us to measure. Dan

[Raggi_Thor]

What's the problem?
Aluminum cans on the bottom doesn't make much harm, I guess.

BUT producing new aluminium requires a lot of energy, so much that aluminum should cost many times more than it does if the aluminium factories paid the same for electricity as we do (at home).
So, recycle, every can, always.

[RolyGate]

Guy I knew used to sail with a marine biologist. He chucked beer bottles over the side whenever he could - said it was the best thing you could do for sea life (filled them first so they sank). Must be for giving the small stuff somewhere to hide.

[timgoz]

The fellows in Alaska crease the can in the middle, then bend it back and forth several times. Then they tear it almost to the bottom. This allows the can to sink and them get the very last sip hiding in the bottom. Beer costs an arm and leg up there.

RolyGate, welcome.


Tim

[mydauphin]

Aluminum does not corrode the same as steel or iron, It does not care about oxygen in water. It corrodes via galvanic actions, the electrons go from aluminum to steel. Aluminum sacrifices itself to Iron or steel. So if Aluminum fails in middle of ocean it could be there almost indefinitely, if it falls next to piles of iron it would be gone in a month. Your mileage may vary. But it doesn't matter Aluminum is the most common metal in earth crust, and in seawater. I don't know about epoxy coating on inside of can or paint on outside maybe that is bad.

[timgoz]

Trust me buddy, if it did not do "something" it would build artificial ridges in the remote Alaskan settelments.

Tim

[Poida]

Why don't you send the question to "Myth Busters"

Poida

[Frosty]

Yeah,--- they could bust the Myth.

And in English.--They would make intelligent experiments to prove or disprove the accusation that alluminium cans last,-- or do not last a long time.

Oh great,--- I have an American spelling checker that does'nt like 'Alluminium' Alluminum Oh Ok.