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Letter 115
Improved process to finish aluminum for
vacuum application
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I am looking for methods to finish Aluminum so they may be used as
sealing surfaces in Ultra High and Medium Vacuum systems. Because
they are used in vacuum systems, they must be cleaned to remove any
machining oils prior to use. Presently the parts are finished with
sandpaper and
0000 steel wool [link is to product info at Rockler]. The desired
final finish is in the 8 range (after cleaning). It appears the parts
are being etched, during cleaning, just enough to degrade the finish.
The only way to get the desired finish back is to polish the surface
with 0000 steelwool. It should be noted that some of the surfaces are
at the bottom of dovetail o-ring grooves which can have an entry
width of 1/8 inch.
Either a different method of finishing or plating is desired. The
present method is too time consuming to be practical. Thanks in
advance for your help!
Marty Kangiser -
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I don't know whether it has real applicability to your particular
need, but aluminum can be bright dipped in nitric-phosphoric solution
to mirror brightness (and commonly is, for reflector use) or it can
be electropolished.
Plating is certainly possible, but it sounds like it may be adding
a complication factor without addressing the basic issue.
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Ted Mooney, P.E.
finishing.com
Brick, New Jersey
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