# Diet drinks and steel cans **URL:** \ **Category:** Factual Questions\ **Created:** [November 17, 2010, 8:11pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015 "2010-11-17T20:11:54Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [November 17, 2010, 8:11pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/1 "2010-11-17T20:11:54Z")
Simple question: Why do diet milkshakes like Slimfast come in steel cans instead of aluminum like everything else? Is there something in these drinks that reacts poorly to aluminum? And aren’t all these cans lined anyway, so it shouldn’t make a difference? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 17, 2010, 8:20pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/2 "2010-11-17T20:20:16Z")
In the case of carbonated drinks, some of the structural integrity is provided by the pressure inside the aluminium can, keeping it rigid. Drinks without sparkle probably need tougher cans. That said, some carbonated drinks come in steel cans too. ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [November 17, 2010, 8:23pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/3 "2010-11-17T20:23:44Z")
Hmm. But I’ve also got some non-carbonated V8 juice that’s in the same kind of aluminum cans my carbonated soda comes in. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [November 17, 2010, 8:30pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/4 "2010-11-17T20:30:49Z")
Those drinks might taste nasty if they are room temp or warm. Perhaps the thicker cans keep them cooler? ---
**Author:** ![Carl\_Pham](https://avatars.discourse-cdn.com/v4/letter/c/e9a140/32.png) [@Carl\_Pham](https://boards.straightdope.com/u/Carl_Pham)\ **Post date:** [November 17, 2010, 8:56pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/5 "2010-11-17T20:56:14Z")
Aluminum itself is quite reactive, but the bare metal forms a thin hard layer of alumina (Al2O3) on exposure to air, and this layer is quite unreactive. Furthermore, anything that will react with aluminum is going to react with iron as well, only less vigorously so. If I had to guess, I would say the economics of the manufacturing process drive the decision. It may simply be easier and cheaper to fill a steel can, or it may be that a heavier can is needed, as noted above, in which case the fact that raw steel is cheaper than aluminum may matter. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [November 17, 2010, 9:32pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/6 "2010-11-17T21:32:27Z")
It _could_ just be a matter of marketing. Maybe they’ve found that Slimfast sells better in steel cans—perhaps because, the cans being heavier, the contents are perceived as more substantial? But that’s a WAG for which I have no evidence. ---
**Author:** ![sitchensis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sitchensis/32/4892_2.png) [@sitchensis](https://boards.straightdope.com/u/sitchensis)\ **Post date:** [November 17, 2010, 9:53pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/7 "2010-11-17T21:53:47Z")
If I had to guess I would have to think it’s the different amount of heat and pressure applied to make the contents safe for storage. Most diet drinks seem to be milk based, I can’t think of any other milk based canned product that is not in a thinker can or a glass bottle. Canned meats, tuna, spam all have stronger cans. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [November 17, 2010, 10:01pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/8 "2010-11-17T22:01:57Z")
> [@Carl\_Pham](#): > > Aluminum itself is quite reactive, but the bare metal forms a thin hard layer of alumina (Al2O3) on exposure to air, and this layer is quite unreactive. Furthermore, anything that will react with aluminum is going to react with iron as well, only less vigorously so. Drink cans have a thin coating of plastic on the inside anyway. ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [November 17, 2010, 10:15pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/9 "2010-11-17T22:15:24Z")
> [@sitchensis](#): > > If I had to guess I would have to think it’s the different amount of heat and pressure applied to make the contents safe for storage. Most diet drinks seem to be milk based, I can’t think of any other milk based canned product that is not in a thinker can or a glass bottle. Canned meats, tuna, spam all have stronger cans. Aha - may be onto something here. ---
**Author:** ![Student\_Driver](https://avatars.discourse-cdn.com/v4/letter/s/3da27b/32.png) [@Student\_Driver](https://boards.straightdope.com/u/Student_Driver)\ **Post date:** [November 18, 2010, 3:15pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/10 "2010-11-18T15:15:54Z")
> [@sitchensis](#): > > If I had to guess I would have to think it’s the different amount of heat and pressure applied to make the contents safe for storage. Most diet drinks seem to be milk based, I can’t think of any other milk based canned product that is not in a thinker can or a glass bottle. Canned meats, tuna, spam all have stronger cans. For several years, Slim Fast drinks were available in non-dairy fruit flavors (orange-pineapple, apple-cranberry-raspberry, etc.) in addition to the traditional dairy-based shake flavors (chocolate, vanilla). Non-dairy flavors were packed in aluminum cans, dairy in steel cans, driving home the difference in packaging each type of drink needs that you’ve pointed out. Oddly enough, the canned Starbucks “double shot” drinks are packaged in aluminum cans despite using milk… not sure what’s up there. There’s been a trend in the last few years for dairy diet/nutrition drinks to switch to PET bottles or aseptic Tetra Pak cartons, rather than steel cans. ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [November 18, 2010, 7:47pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/11 "2010-11-18T19:47:23Z")
> [@Student\_Driver](#): > > Oddly enough, the canned Starbucks “double shot” drinks are packaged in aluminum cans despite using milk… not sure what’s up there. Maybe, in the Starbucks case, the milk is already steamed to near-boiling and mixed with the coffee, just like it would be when ordering a regular latte/mocha, _before_ it’s put into the cans, whereas the diet shakes are heat-treated _after_ they’re canned? Just a WAG. Also, coffee’s acidic nature is less conducive to bacterial growth (_any_ acidic food is less favorable to bacteria, which is part of why you don’t have to refrigerate things like catsup and mustard). ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [November 20, 2010, 6:13pm UTC](https://boards.straightdope.com/t/diet-drinks-and-steel-cans/561015/12 "2010-11-20T18:13:24Z")
I’ve wondered why [Wittekerke (RateBeer link)](http://www.ratebeer.com/beer/wittekerke/9315/3/1/) is sold in steel cans, too.