[TheForge] aluminum, zinc, or other revisited.

[terry l. ridder]

hello;

this is an update concerning determining what metal the case of a hard drive
is made of, aluminum, zinc, or other. after much research and testing
with various of the cases on hand. i have a good way to determine the type
of the metal.

the first test is for magnesium.
this test just requires vinegar/ acetic acid.

the chemical formula is:
Mg  + 2 HC2H3O2 ====> Mg(C2H3O2)2 + H2 + Heat

so far i have found two hard drive case made from magnesium.

the next test is for aluminum.
the test just requires methanol/ methyl alcohol.
methanol is corrosive to aluminum.

the chemical formula is:

methanol, a weak acid, attacks the aluminum oxide that normally protects
aluminum.

6 CH3OH + Al2O3  2 Al(OCH3)3 + 3 H2O

quoting from wikipedia concerning methanol.

The resulting methoxide salts are soluble in methanol, resulting in clean
aluminium surface, which is readily oxidised by some dissolved oxygen.
Also the methanol can act as a oxidiser:

     6 CH3OH + 2 Al  2 Al2(OCH3)3 + 3H2

So the corrosion continues until the metal is eaten away

my source of methanol is the winter gasoline additive heet.
basically, pure methanol.


yet another test is to help further sort out the cases.
the test just requires muratic acid. 30 % hydrochloric acid.

many metals react with hydrochloric acid to form the
metal's salt and hydrogen gas.

the amount of hydrogen gas generated and the rate it is generated is
a characteristic of the metal.

zinc, will react almost immediately to hcl.
aluminum, reacts slowly at first than violently after the protective oxide layer
has been dissolved.

Mg(s) + 2HCl(aq)  > MgCl2(aq) + H2(g)

Zn + 2 HCl        > ZnCl2 + H2

Al(OH)3 + 3 H3O+  > Al3+ + 6 H2O

or

Al2O3 + 6 H3O+        > 2 Al3+ + 6 H2O

Al + 3 H3O+        > Al3+ + 3 H2O + 3/2 H2

2Al(s) + 6HCl(aq)  > 2AlCl3(aq) + 3H2(g)

i made a crude hole saw the diameter of a dime. i use these small samples for this
test.

the reactivity of the three metals magnesium, aluminum, and zinc react in that order.
magnesium is more reactive than aluminum and zinc.
aluminum is between magnesium and zinc in reactivity.
zinc is last amongst the three metals.


these simple tests are much easier than weighing each case and
determine its volume then density.
there are a number of cases which are definitely alloys of aluminum
and magnesium. they react with both vinegar and methanol.


there are a small number which are zinc based alloys. those i have set off
to the side.

so i have remember some chemistry i had forgotten from school.
determined with reasonable tests the aluminum cases.
so all was not lost in pursuing sorting out the hard drive cases.

i am still refining the tests and looking for further tests to provide
more infomation concerning the possible alloys used to make the cases.


i have clearly labeled the magnesium cases so that they are not mistakenly
brought close to an open fire. i do wonder why the  cases were made of
magnesium to begin with.


thank you for your time.

-- 
terry l. ridder ><>