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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Gold Chem-Film Finishing Different Shades
Currently in our chem film line we dip our sheetmetal parts consisting of steel and aluminum and sometimes parts on the same rack will come out in different shades. Does anyone know the reason for this?
Josh ValliereShop Employee - Cedar Rapids, IA, United States
January 14, 2009
Hi, Josh. Solution agitation is important for consistent color. Do you have air agitation or solution spargers? Tell us more about the presence of steel in this bath.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 27, 2009
First of two simultaneous responses --
The reference to steel and chem film puzzles me as well, but I have found a good amount of variation in color due to alloy, surface finish (sanded vs blasted vs mill finish), and even though they go through the same process to clean, if one part had more in the way of soils or lubricants prior to clean, and now has some residues remaining in Chem-Film or affected prep in interim steps. More info would be good.
Paul Slater- Cedar Rapids, IA, USA
January 28, 2009
Second of two simultaneous responses --
Iron contamination in the chromate solution will degrade corrosion protection, enough will fail salt spray testing.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
January 28, 2009
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