Why are beverages sold in aluminum cans, other goods in steel cans? 13

[Christine74]

Can anyone explain to me why beverage cans are fabricated exclusively from aluminum, while other goods (soups, vegetables, etc.) are usually packaged in steel cans?

Does it have something to do with carbonic acid corrosion? Just wondering.

Thanks,

-Christine

 

[CoryPad]

Item 1: Beverage containers are sealed with internal pressure (either carbon dioxide for carbonated drinks or nitrogen for juices and the like).

Item 2: Food containers are sealed with a vacuum (to prevent oxygen from accelerating spoilage).

Item 3: Beverages containers typically are a two-piece design (one body and one end).

Item 4: Food containers typically are a three-piece design (one body and two ends).

Item 1 means beverage containers are small pressure vessels and need to be strong enough to resist the resultant hoop stress from pressurization. Aluminium alloys have been found to provide adequate strength for the containers.

Item 2 means food containers need to be strong and STIFF to resist wall buckling due to external forces. Here, aluminium alloys have not been found to be as good as steel.

Item 3 means that the body is deep drawn from sheet. The aluminium alloy does not strain harden or strain rate harden, which means the forming forces are less than those for steel, which makes for less expensive manufacturing.

Item 4 means the body is produced by wrapping sheet (typically corrugated to improve stiffness) into a cylinder and welding it. Aluminium alloys are not as easy to weld as steels.

By the way, outside of the USA, steel beverage cans still account for up to 50% of the market.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Rjeffery]

Aluminum also conducts heat much better so it is easier [read more efficient] to cool liquids in Al than in Fe

The best way to test something is to squeeze it, slowly, until it breaks!

 

[EdStainless]

and ALL cans for bev and food are coated on the inside. Often shelf life is limited by the coating and not the product.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[RPstress]

I have seen a mix of Al and steel used for beverage can bodies. The pop-top is always Al, but it seems to depend on immediate market price or something similar for the choice of material for the body.

Recently most if not all beverage cans have been Al. I haven't seen a steel one for over a year.

A lot of recycling of beverage cans depends on the body being Al. Since it's hard to the difference, this can be complicated by using steel. With practice you can tell by feel: the steel cans have a bit more weight at the bottom. There's also usually a coating on the outside of the bottom with steel, rather than the bright Al bottom finish.

 

[KENAT]

Or as Blue Peter (UK kids TV programme) taught me when they had an Al can drive.

You can check which is which with a magnet, the steel will be attracted to the magnet. If you don't have a magnet use the strip on a fridge door.

Off topic though, sorry.

KENAT, probably the least qualified checker you'll ever meet...

 

[stanweld]

You really must go back in time and look at the pricing of the 2-piece aluminum can vs the 3-piece tin plated steel can. There was some predatory pricing by the aluminum can industry back in the late '60's and early '70's. This as well as consumer preference effectively spelled the demise of the steel can in the beverage industry in the USA.

We in the steel industry tried competeing with a 2-piece drawn & ironed can in the early '70's but most of the steel making practices in the US mills at that time could not produce steel that could meet the deep drawing properties required.

 

[jte]

Aluminum also conducts heat much better so it is easier [read more efficient] to cool liquids in Al than in Fe

Rjeffrey-

I presume by "more efficient" you meant more efficient with respect to time, not energy. Unless I'm mistaken, taking X BTU's out of a can of warm beer should take the same amount of energy regardless of whether its steel or aluminum (discounting the sensible heat of the metal itself). The beer in the aluminum can may cool faster, but the beer in the steel can must lose an identical amount of heat to cool to the same temp. In fact, since doing things slowly tends to be more energy efficient than doing things quickly, cooling a steel can of beer may be more energy efficient...

Thoughts?

jt

 

[IRstuff]

You guys seem to missing something.

Aluminum can = pull tab. Steel can = no pull tab. The pull tab has been the hallmark of aluminum cans from the start, substantially increasing the convenience of drinking from cans, making us all a bunch of fat boozers ;-)

Steel cans can only support complete removal of the top of the can; try drinking your beer with that!

TTFN

FAQ731-376

 

[stanweld]

A little more history.
The heavy metals (lead & bismuth) in the solders to join the tin plated steel can body were being scrutenized by the media (health hazard) during the late 1960's. This promoted aluminum can use even more. To meet the "no-solder" criteria, ConCan and American Can developed a welded steel can body and an adhesive bonded steel can body for beverage containers. The welded can body was chrome plated (hexavalent chrome anyone?).

While the steel industry could not make the two piece container for beverages, it soon could produce two piece tin plated cans for soup containers (prodded by Soup producers)and a variety of containers for other goods where the drawing requirements weren't so severe.

By the way, pull tabs were available on steel body cans. They were originally adhesively bonded to the top but the pull tab had to be removed and discarded.

 

[CoryPad]

IRstuff,

Your post does not make sense. Beverage cans used to use pull tabs that needed to be discarded, but Stay-On-Tab's have been standard for more than 30 years.

http://www.lva.lib.va.us/whatwedo/archweek/2005/VHS/VHS_5.htm

Steel ends can be made with a pour panel:

http://www.sonoco.com/sonoco/Products/Easy-open+ends/con_steel_beverage_ends.htm

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[btrueblood]

And before pull tabs was the church key, no need to rip the tops off...and punching a seperate small vent hole on the opposite side from the drinking hole made the beer pour more quickly...

http://en.wikipedia.org/wiki/Church_key

 

[IRstuff]

They make steel pour tabs, NOW, but not 30 yrs ago. The steel used 30 yrs ago for cans were substantially stiffer and small openings could not be opened without a windup key, ala the old Spam cans. If anyone remembers, even the skinny little sliver that opened a Spam can took a LOT of work. Imagine trying to open something with 3 times the width, requiring 3 times the energy to open.

The whole point was a question of convenience. Aluminum cans won the battle because they required NO external tools, ala church keys, and no windup keys. You pull the tab and you're ready to drink. No fuss, no muss.

TTFN

FAQ731-376