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Passivation with trivalent vs. hexavalent chrome

Dear All

I am Shay, a New chemist to the field; came to electroplating from pharma.
I have found out that Hexavalant Cr coating has better abrasive resistance than Trivalent Cr.
Anyone could assist with comment of review regarding the differences and properties of the two Cr passivations? ideas of improvement of the RoHs trivalent Cr passivation.

Sincerely yours

Shay Ben-Menachem
research - Israel
December 2, 2010

P.S.: New chemist in the field with Pharmaceutical Background. Enjoy Gardening with my wife. I wish her to see this remark, but she is a social worker so will probably not like this page :-)

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Hi, Shay.

Generic trivalent chromates has been around for decades and are, in general, not very satisfactory because of minimal corrosion resistance. When people speak of trivalent chromates today, they are usually speaking of highly developed and highly proprietary systems that offer roughly the corrosion resistance of hexavalent chromates. Some of these use topcoats, some don't -- and some presumably have greater abrasion resistance than others. If you look at other brands you may find a more abrasion resistant coating. None of them, to my knowledge, offer the "self repairing" of scratches like hexavalent chromates though.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 2, 2010

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March 1, 2011

Thanks for the detailed answer, Ted.

Is there any good company you know that I could apply to?
I woul need the following:
1.Good passivate (ROSH) that will good adherance to organic paint (resin and polyurethane based)
2.Good passivate (ROSH) for bolts and fasteners >72h salt spray

Many thanks
Shay

Shay Ben-Menachem
- Israel

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Hi, Shay.

We don't recommend specific suppliers here, but all of the major suppliers offer good proprietary trivalent chromates: Atotech, Chemetall, Heatbath, Henkel, Luster-On, Macdermid, Surtec and several others.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 1, 2011