plating, anodizing, & finishing Q&As since 1989
What is zinc dichromate type II class 3?
What is zinc dichromate type II class 3?Bantine Lee
Sinjung - Chung wa, Taiwan
Type II generally refers to colored chromate conversion coating applied to zinc following plating. Class 3 most likely refers to the thickness from a specification callout such as the former QQ-Z-325 for which class 3 denoted a minimum thickness of 0.0003 inch ( or about 5 micrometers ). You really need to go back to whoever wrote the finish callout and get their interpretation of the callout; if this callout came in on an order to my shop (and we do get several strange callouts like this), I'd put the responsibility of defining the coating back on my customer ( and not on some internet hacker that has nothing better to do than respond to finish.com letters! )
Milt Stevenson, Jr.
Syracuse, New York
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