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Can a Type II and Type VI zinc plate per ASTM B633 be the same chemistry?

September 16, 2009

Here is my situation: we callout to zinc plate a part as "Zinc plate per ASTM B633, Type II, SC-3, Color: Black." On a recent check of our plating houses certifications, they have the zinc plate listed as a ASTM B633, Type VI. They told us that the chemistry they are using is correct and can be certified for both the ASTM B633 Type II (w/ colored chromate coatings) and the Type VI (with colored passivate).

Can the same chemistry be used for both types? I assumed they would be different as one lists in the ASTM spec as a colored chromate and the other as colored passivate, but they insisted that the chemistry for both can be the same, and that Type VI just is to ensure ROHS compliance due to being hexavalent free.

Please let me know if this is correct. Thanks!

Josh Griffin
Product Engineer - Gilbert, AZ USA