Clear Alodine. Perhaps Alodine 1500 per MIL-C-5541C, Class 3?
I'm not sure that reliable data exist for the loss tangent and dielectric constant. The only electrical property usually measured is the contact resistance for MIL-C-5541C, Class 3 coatings. The maximum contact resistances allowed are:
5000 micro-ohm/sq. in. (after 24 hrs cure at 70-90[sup]o[/sup]F, and
10 000 micro-ohm/sq. in. (as above, plus 168 hrs salt spray per ASTM B117).
See thread332-136478 for more info.
You can maybe figure out a dielectric constant from the resistance, measurement paraameters & coating thickness (extremely thin, I'll have to look it up).
Ken
Alodine is a very thin metal pretreatment based either on chromate or new titanium-bearing compounds. In general, Alodine has "medium" resistivity.
Anodizing is a process that creates an oxide layer from the base metal. It can be thin (but still much thicker than Alodine) or thick. In general, it has high resistivity.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.