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Letter 27076
Need process for 108 hours in CASS Test
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We have plated 25 micron medium phosphrous electroless nickel as
under coat and 10 micron micro craked chromium as top coat. At CASS
test it has failed after 44 hours against the requirement of 108
hours. Please adivse us what process can withstand up to 108 hours in
CASS test.
K. Jagan
Director - Coimbatore, Tamilnadu, India
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You should use an electroless nickel
containing at least 10.5% P for severe corrosion services such those
requiring CASS tests. Also, to obtain 104 hours resistance, you will
probably have to increase the coating thickness to 50 or 75
microns.
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Ron Duncan
Palm
International, Inc. -
LaVergne, TN
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Ed. note:
It is our sad duty to alert the readers to the passing
of Ron Duncan on Dec. 15, 2006. For those who would like to
know more about him, a brief obituary opened
Update No. 13 of our
Metal Finishing Industry Update Podcast.
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The recommendation from Mr. Duncan seems correct, since high phos
EN is more resistant to corrosion and has less pores or voids.
Although, another thing to keep in mind, besides porosity or
discontinuities is that EN is hard. This means that the microcracks
in this particular chrome, which were developed for ductile
electronickel or copper underplates, might propagate through a
fragile layer to the base metal.
Guillermo Marrufo
Monterrey, NL, Mexico
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