Help with Zinc-Nickel per AMS2417 Type 2

I have some 4130 Steel parts that are being zinc-nickel plated per AMS2417 Type 2. When they were sent in from my supplier, there were little scratches through the chromate coating.

How can I tell if the scratches have also gone through the zinc-nickel coating without running full 500-hour salt spray testing?

I think 500 hrs has passed since your inquiry, but better late than never, eh? The copper sulphate ⇦ on eBay or Amazon [affil link] or the ferroxyl test might work here.

Alternatively, profilometry could be used to determine scratch depth and if the scratch is less than the coating thickness you should be okay.

A little off-topic, but even if the scratch is deeper than the coating, you still might be okay. We've used a SEM to characterize the surface of hand-scribed test coupons and found it can be quite difficult to break thru a ~0.5 mil electroplate. Test coupon scribe variability was so great that it confounded and essentially ruined salt fog test results. We have since adopted a repeatable machining technique for scribe creation in our galvanic corrosion tests.

Regards,

adv.
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