[Milsurplus] Satin finishing aluminum

[jhaynes@alumni.uark.edu]

Here's a quotation from the 1954 ARRL handbook

"Aluminum chassis, panels and parts may be given a sheen finish by
treating them in a caustic bath.  An enamelled container, such as a
dishpan or infant's bathtub, should be used for the solution.  Dissolve
ordinary household lye in cold water in a proportino of 1/4 to 1/2
can of lye per gallon of water.  The stronger solution will do the
job more rapidly.  Stir the solution with a stick of wood until the
lye crystals are complete dissolved.  Be very careful to avoid any
skin contact with the solution.  It is also harmful to clothing.
Sufficient solution should be prepared to cover the piece completely.
Whem the aluminum is immersed, a very pronounced bubbling takes
place and ventilation should be provided to disperse the escaping gas.
A half hour to two hours in the solution should be suffcient, depending
upon the strength of the solution and the desired surface.

Remove the aluminum from the solution with sticks and rinse thoroughly
in cold water while swabbing with a rag to remove the black deposit.  
Then wipe off with a rag soaked in vinegar to remove any stubborn
stains or fingerprints.  (See May, 1950 QST for a method of coloring
and anodizing aluminum.)"

The yellowish aluminum seen in a lot of military stuff is the result
of a "chromate conversion coating" but I don't know any more about it.