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Mottled surface appearance of hard coated 6061 AL after repeated autoclave cycles

2006

Our product is a container that goes through repeated autoclave cycles (~250F). The part is made from 6061 AL and is hard coated. It is neither dyed or sealed. The parts initially are uniform dark grey and have measured coating thickness around 2 mils.

After a few autoclave cycles the appear mottled in color. There are distinctly different, random shades of grey. The initial response was dye was leaching out. Except we the parts are not dyed.

Any help would be appreciated.

Gary Bernier

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One trip thru the Autoclave would permanently 'seal' the coating.
Other than H2O is there anything else in your sterilization process? Anything with a high ph perhaps?

Bill Grayson
metal finishing - San Jose, California
2006