That all makes sense.
We are certainly using a thick-film passivate, but our supplier is calling it a chromate. (SC2 is 8000 nanometers minimum)
However, we aren't using any organic seal or other topcoat. That must be what's making the difference in the salt spray tests.
I'm revising an old Fe/Zn plating spec that currently calls for "Trivalent Alkaline Zinc plating per ASTM B633 Type II (yellow) SC 2." The revised spec should prohibit the use of Hexavalent Chromium, which is the intent of the word "Trivalent" now.
Would the preferred method of doing this be...
