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Letter 39029
Alternative to zinc and colour customer
asking for trivalent finish on future orders
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please can you help?. we are a enginering company supplying mild
steel studs to varios industries.Some customers who currently we
supply zinc & colour are requiring trivalent finish on future
orders.What does this meen and what colour is it.
Thanks in advance .
KL Smith
skm products - Leleicester, England
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Okay, K L, the main purpose of "colour" on top of zinc plating is
corrosion protection by application of chromate, rather than
aesthetics. So when you say you supply "zinc and colour" what you
really mean is that you provide a coating that includes zinc plating
and color chromating. The color is usually yellow (actually more like
amber or honey).
These yellow chromates have traditionally been based on hexavalent
chromium which is a toxic compound now forbidden by RoHS and other
standards. So what you now need to do is have your plater apply
"hexavalent-free" passivation processes after the zinc plating. These
are usually inherently colorless, but proprietary coatings are
available that are yellow in color if that is essential.
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Ted Mooney, P.E.
finishing.com
Brick, New Jersey
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