On Thu, 05 Jul 2012 05:52:37 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

"Wild_Bill" fired this volley in
:



I dunno what the composition is, but truck owners use a chemical
solution to remove oxidation from those pretty uncoated aluminum dump
beds and trailers.

Phosphoric acid is best used on ferrous metals. Any kind of acid is the
wrong choice for aluminum.

Bases are most effectively used to clean aluminum. Truck wheel cleaner,
AC evaporator cleaner, and sink drain un-plugger are all the same stuff;
potassium hydroxide or sodium hydroxide in solution with water and some
detergent.


The caustic concentration must be very low in those products. I
worked on caustic soda production in R&D decades ago. In 10% NaOH
solution, aluminum very actively reacts, releasing hydrogen gas.

Don't use lye on your aluminum.

Pete Keillor

Acids preferentially attack the metal while leaving the oxide intact
until the metal undercuts the oxide, and it just falls off the surface in
pieces.

Bases preferentially attack the oxide very rapidly, actually dissolving
the Al2O3 while slowly attacking the metal.

AND, I think you have not a clue what aluminum oxide looks like, or you'd
not have made this statement --

In my experience with diluted phosphoric acid solutions used to etch
metals, the metals are not susceptible to immediate, or quick,
oxidization after treatment.

Bill, aluminum oxide, when it forms on _clean_ aluminum, forms in mere
seconds (just two or three, really), and is perfectly transparent and
clear ("water white" is the term that combines both).

Although impurities make them colored red or blue, you do know, don't
you, that rubies and sapphires are aluminum oxide -- right?

The "nasty-looking stuff" you see on corroded aluminum is NOT aluminum
oxide, but salts of aluminum remaining from other attacks on the metal
besides from oxygen -- like chlorides or phosphides.

LLoyd