Not sure this is the best forum for this question but a search of this site for 'zinc plate' showed posts in many forums with no obvious favourite.

I have an engineer that needs a corrosion/protective treatment for a steel part.  I've suggested zinc plate, it's in a fairly benign environment but may see some occasional slight wear/abbrasion.  It needs to be ROHS compliant, so no hexavalent chromium in the I've done a bunch of google searches and arrived at the below.

ZINC PLATE ASTM-B633 Fe/Zn 8 (Type III, SC 2, .0003-.0005 THICK, CLEAR) ROHS COMPLIANT.  DIMENSIONS APPLY AFTER PLATING.

Is this the (a) correct way to designate this finish?

I realize the details in () probably duplicate what's given by the Fe/Zn 8 but I want it to be clear for all users and some of the treatment company sites only listed the type & service condition.

We don't call up much zinc plating so I can't readily justify actually getting the spec at this time.

Thanks,

KENAT,

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Typical designation:

ASTM B 633 Fe/Zn 8 Type III SC 2

You don't need the thickness numbers unless you need to limit the maximum thickness (the 8 is 8 micrometers minimum).  You don't need to specify CLEAR since Type III is colorless chromate conversion coating.  ROHS COMPLIANT is intended to restrict the conversion coating to only trivalent chromate rather than hexavalent.  I would state that directly.

Regards,

Cory

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Thanks Cory, so the TYPE III & SC2 should be out of the parenthesis then, that's what I couldn't work out from the sites I looked at.

The clear is as much for our receiving department as for the vendor, hence in parenthesis.  On the thickness I do believe we need to limit the max thicknes, .0005 would take it up to the next class which is why I set it as the max value, though arguably then it shouldn't be in ().

I'll change the wording on the Hexavalent/Trivalent/ROHS.  I've never been happy just putting "ROHS" but have been directed to do that before on similar notes.

Thanks a lot.

KENAT,

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I agree that you should directly specify "trivalent chromate" on the drawing.  "RoHS compliant" is essentially meaningless if there is no reference to a standard.  ASTM B 633 was created a number of years ago, and therefore has not incorporated anything related to reportable/restricted materials, RoHS, etc.   

ZINC PLATE ASTM-B633 Fe/Zn 8 Type III SC 2 (.0003-.0005 THICK, CLEAR).  FINISHED ARTICLE TO BE ROHS COMPLIANT, NO HEXAVALENT CHROMIUM TO BE USED IN CONVERSION COATING.  DIMENSIONS APPLY AFTER PLATING.

Updated wording, I'm uncomfortable explicitly saying use trivalent in case they come up with something else, however I have explicitly forbiddien hexavelant which I understand to the be trouble maker.  TVP that's exactly the reason I don't like just saying "ROHS", it doesn't explicitly invoke a standard.  Plus China ROHS is slightly different from EU ROHS legislation etc.

KENAT,

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