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Difference between mill finish aluminum & chromatized finish

What is the difference between mill finish & chromatized finish in aluminium? kindly explain if anybody knows.

Thiru Venkadam
facade design engineer - Bangalore, Karnataka, India
March 19, 2011

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Hi, Thiru.

To the best of my knowledge, "mill finish", means the natural finish that is achieved by the mill when they roll, cast, or extrude a product. In other words, no effort has been made toward improving the finish. "Chromatized" is slang rather than a specification, and as such, there is always the possibility that one person meant something a bit different than the other guy, but I would interpret it to mean that the aluminum was chromate conversion coated; one example of a specification for chromate conversion coating of aluminum is Mil-DTL-5541. This would generally imply that a multi-step process has been performed on the aluminum that cleans and desmuts it prior to the application of a chromate conversion coating that renders it uniform in appearance, reasonably corrosion resistant, and with a base layer suitable for adhesion of paint.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 21, 2011