Before Al cans became popular cans were made out of steel (outside the 45% still

Question

Before Al cans became popular cans were made out of steel (outside the

45% still are). Sodas are highly acidic and thus to avoid corrosion a Zn

coating had to be applied. Given your current understanding briefly answer

the following questions:

a) Why do you think Al replaced steel cans? (Consider only the

material properties that we discussed so far).

b) Which material would you prefer if you wanted to carbonate your

drink more?

c) The pressure more than doubles when you go from 4 degrees

centigrade (p=117 kPa) to 16 degrees centigrade (p=276 kPa).

How would this knowledge affect your materials choice if your

soda can (355 ml at 4 degrees centigrade) was to be heated to 61

degrees centigrade

Explanation / Answer

a)al readily oxydizes to form a thin layer of Al203 but unlike the corrosion in steel(or iron specifically) this layer is impervious and thus prevents action of any other substance( here carbonated water).Thus ,being cheaper and more stable ,al can replaced steel cans

b)carbonating drink more means making it more acidic.thus, we will prefer the one which is lesser reactive.

c)If pressure increases drastically with temperature we must prefer steel can because aluminium can cant handle so much of pressure

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