How does aluminum rust?

[D2Cat]

When I leave for the day, I usually take a cooler with me for liquids and lunch. I almost never eat out. In my cooler I usually have a can of diet pepsi, a small can of regular soda, couple containers of water, sandwiches, chips, cookies...whatever.

The other day. after being sick for a few days, I went to empty any melted ice and replenish the cooler. I found a couple of inches of "dark water" among my water bottles. Upon further inspection this is what I found.

The pepsi can completely empty with the top still sealed.

So is this caused by the recyclers missing some steel scrap as the alum. goes through the grinder and eventually gets melted in with the alum, thus causing the rust?

Any metallurgist out there to clear this up?

 

[85Hokie]

nothing rusts but IRON!

now - lots of stuff oxidizes ........silver = tarnish, alum - white power, copper = green.....

I am in electrical class - talking about the best conducts out there, get into gold and silver and copper and what not......

GOLD is not the best conductor, damn close - but it does not oxidize like others....that's why stereo stuff is plated, NASA uses gold connections for the same reasons.

That can looks like the soda - which is an acid, left behind that "rust" - now how the soda got OUT of the can ....mmmmmmm....

I have bought a few cases of "drinks" and over the last 50 years- had a few half full - and or empty! Empty can of nuttin!

 

[coachgeo]

My guess is ice was made with real hard water. As it melted the minerals in the water bound to aluminum or caused corrosion. Esp. if traces of any acid was already in cooler from past soda spills/leaks.

 

[conropl]

With can recycling, the can is heated to burn off the graphics and inner plastic coating; then they are crushed; and then thrown in a melter (furnace with a lot of agitation). Iron melts at a much higher temperature that Aluminum and would never melt. Aluminum would likely oxidize it over time, but it would settle out on the bottom. It is filtered prior to being poured into an ingot form which would further eliminate any chunks. The ingot is then rolled into sheet that is only 0.005 thick (I think the can forming process stretches it down to 0.004")... so inclusions of foreign material in the can are tightly controlled or the can would fail.

Iron in the metal is very unlikely. However, the acidic pop (soda for you easterners that get mad when I call it pop) will corrode aluminum. That is why the inside is coated with a plastic. If the pop leaked out, it would attack the can on the outside. In college, being a board young man, I took a can and soaked it in muriatic acid to see what it would do. It dissolved it quickly, and all that was left was a plastic bag (the inner coating).

Hard to tell, but it almost looks like the is a crack along the bottom edge (or it is just a stain). Did the can freeze at some point and crack the bottom? In any case, however the pop got out, that is what would likely cause the can to corrode.

 

[Lil Foot]

And any corrosion would be accelerated if any dissimilar metal was in the same liquid. Any steel or iron in the cooler? (fork, spoon, knife, 1911, machete?)

 

[bearbait]

I find if you mix a little alcohol with it you won't have any problem.

 

[Newlyme]

Here is what most likely happened.
The can was damaged somehow and cracked the coating on the interior of the can.
The pop ate it's way out. Phosphoric acid.
I work for a much larger beverage company and worked in their bottling plant for ten years before transferring to something with a little slower pace. The filler on the can line runs at 1,850 cans per minute. You can only imagine how many cans would get stuck in the machine between the time one jammed and the operator hit the E-stop!
Those cans are getting thinner all the time.

 

[OldeEnglish]

Imagine what that stuff does to your teeth , I know for a fact it will eat right through cast iron pipe. When we pipe drains off of soda fountains, they have to be PVC until a point of dilution where there is enough water to dilute it. I've had a few instances where they were tied into cast iron with out enough water to dilute it and it ate through it like it was straight acid. I prefer water or beer myself, or if your a light beer drinker you get the best of both worlds.

 

[Newlyme]

When we pipe drains off of soda fountains, they have to be PVC until a point of dilution where there is enough water to dilute it. I've had a few instances where they were tied into cast iron with out enough water to dilute it and it ate through it like it was straight acid.

And do you see what happens inside the PVC pipe?
It doesn't eat the pipe but that sugary slop sure can grow!

 

[North Idaho Wolfman]

I find if you mix a little alcohol with it you won't have any problem.

Now your on the right track!

 

[Kubota Newbie]

Uhhhm.... So what do you do, and where has your lunch box been? There are few things that cause a rapid degradation of Aluminum as the oxide that forms on the surface of aluminum is self-sealing so to speak and generally inhibits or significantly slows further oxidation (what we all term as "rusting" is just oxidation of iron based metals). Anyway... one of the culprits in overcoming the protective oxide and causing rapid oxidation of Aluminum is Mercury, and apparently Mercury Chloride as well. Neither are things you'd want to have around a lunch container.

 

[D2Cat]

This is a cooler with inside dimensions of 8'x11' and 8" deep plastic probably made for a couple of 6packs with a handle on top. Several years old. Gets cleaned with Clorox and water every couple of weeks. Sometimes the diet pepsi will set in there for several days before it gets consumed. Maybe dumping the ice on the can over several occasions cause the failure.

 

[Russell King]

Good Lord! Just how big a man are you to have a 8 foot by 11 foot lunch box???

lol I know you meant inches just couldn't pass up the opportunity for a stupid comment


Sent from my iPad using Tapatalk

 

[dandeman]

Electrolysis between dissimilar metals is taking place, in your case the aluminum became the sacrificial metal.

This is a huge problem with marine equipment, sea going ships.....

Amen! I used to think aluminum didn't corrode, until I served 1 1/2 years on this ship and frequently saw the white chalky corrosion at certain places on the aluminum superstructure.

Aluminum superstructure construction above the main deck.. and the aluminum life line stanchions were always breaking at the weld to the deck.

We were warned to never lean on or otherwise trust them at sea.

 

[D2Cat]

Hey Russell, I had everything typed out and ready to submit when the phone rang. While I was talking I realized I didn't put any "inch" marks by the numbers.....then what happens.....you caught me!!

 

[BWXT]

Now your on the right track!

Only time I drink soda is if there's an appropriate amount of Cap'n Morgan in it!

 

[D2Cat]

Hudson, I'm going to quit putting cans of "pop" in there!!!!

But then you ought to see what's on my hand half the time, I grab some chips!