cleaning keyboards in the dishwasher

Chuck Guzis cclist at sydex.com
Mon Jan 9 23:33:58 CST 2006


On 1/9/2006 at 11:20 PM C Fernandez wrote:

>Normally, I wouldn't mistake aluminum for steel, but this was a well 
>used restaurant pizza pan that had a thick build up of carbonized 
>oil/grease on it, so it felt heavy enough to be steel!

Just what I wrote earlier.  Aluminum, zinc and magnesium all react with hot
water to form a hydroxide, liberating hydrogen as a reaction product.  

The reason your aluminum pots don't dissolve when you boil water in them is
because aluminum (and zinc and magnesium) form a thin, very tough layer of
oxide which seals the metal suface from the action of the water.

One of the classic freshman chemistry demonstrations is (or was) to immerse
a piece of aluminum under a pool of mercury, with hot water poured on top.
The aluminum has its layer of oxide removed with a bit of sandpaper and
when the metal is raised out of the mercury into contact with the hot
water, it reacts with the water, producing bubbles of hydrogen gas.  This
is also why one doesn't put out a magnesium fire with water, by the way.

When a moderately strong base (such as sodium phosphate or sodium
carbonate)  is hydrolized in hot water, the basic solution attacks the
oxide on the surface of the metal, forming a soluble salt, exposing the
underlying metal to the action of the water.  If the base is very strong,
such as lye, the water needn't even be hot; which is how good old Drano
works (nothing more than lye and aluminum granules); the reaction produces
enough heat,  which coupled with the action of the now-hot lye acts on
grease and protein to clear blockages.  

All of which goes to saying why you shouldn't put aluminum,  magnesium or
zinc (including galvanized hardware) in your dishwasher with dishwashing
detergent.

Cheers,
Chuck





More information about the cctech mailing list