Wes Stewart wrote in message
...
On Sat, 16 Jul 2005 00:30:33 GMT, "RadioGuy"
wrote:
Howdy:
Its been a common practice with me to finish the aluminum surface of a
chassis or box with an immersion into a caustic solution followed with a
coating of clear acrylic spray---I like the satin finish it produces. I
normally use lye that I regularly found on the shelves of our
neighborhood
hardware stores. However, I've been having a harder time of finding the
flaked lye that I have used over the years for that purpose. I have used
'Lewis Red Devil Lye' that I found at Ace Hardware.
I still have a couple of cans of Red Devil "in stock" after my last
project. That was the rejuvenation of a 20-year-old Yagi antenna. I
built a plastic sheet lined trough outside that was long enough to
hold the longest piece of tubing and had at it.
I never thought of that for long pieces... thats a good tip.
A project that I am currently working on made me think of trying a
substitute for lye with an item that I seem to find everywhere. Often
found
in the automotive stores is a product that is referred to as a
'cleaner/degreaser' or 'heavy duty industrial cleaner'. I have seen it
marketed as 'Purple Stuff' yet I purchased a gallon called 'Right Stuff
(Purple Stuff Concentrate)' manufactured by Sunbelt Chemicals, Palm
Coast,
Florida, 386.446.4595. Nevertheless, the contents of both bottles have a
characteristic purple color and contains (besides sodium hydroxide) a
component derived from citrus---but more importantly, the label states
that
the product is NOT TO BE USED ON ALUMINUM!
I finished the surface of both halves of a mini-box by immersing them
into a
solution, by volume, of 1 part 'Right Stuff' to 8 parts warm water (I
used
1:8 for no particular reason---It just happened that way). The surface
of
the aluminum began to bubble rapidly, but not uncontrollably, causing a
fine
white froth to appear on the surface of the solution. I let the mini-box
soak for 30 minutes whereupon I removed them and placed them into a
bucket
of water. I found that the removal of the black residue is easier to
achieve if I wash the aluminum parts while they remain under water---a
sponge or cloth works fine and a Q-Tip removes the residue from corners.
I
observed that as the reaction proceeded the purple color of the solution
became clear.
Good to know. You might find that a dip in vinegar will help with the
removal of the black smut.
Thanks... I didn't know that! I often wondered if there was an easier way
to remove the black residue.
Needless to say, I am entirely satisfied with the results. The dilute
solution of 'Right Stuff' provided a uniform satin finish identical in
appearance to a solution of lye (sodium hydroxide). If you can't find
lye I
suggest a solution of industrial cleaner possessing caustic properties.
The
next time I use 'Right Stuff' I will increase it by 1 part just to see
the
result. The reaction liberates hydrogen gas---use adequate ventilation.
If you want a really satiny surface, another trick I have used is to
sand the surface with an orbital sander and medium grit wet-dry paper
lubricated with light oil. It's a messy process but leaves an
interesting surface with the little "orbit" scratches and it's a good
way to recover badly scratched surfaces. Etching afterwards with lye
"softens" the effect and of coarse cleans the surface.
I'll give that technique a try.
Awhile back I heard that after the metal is finished in a lye bath then
boiled in a solution of color dye (RIT) a colored, metallic finish, can be
produced---one of these days I'll try it on a scrap piece.
On simple projects I print or photocopy text then affix them onto to the
aluminum surface (after a first coat of acrylic on the aluminum) with white
glue then with multiple sprays of acrylic affix them permanently to the
surface. It worked real nice with a bandpass filter project---I secured the
graph of the filter characteristics onto the minibox for reference.
RG
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