7050-T7451 AMS 4050 won't take Alodine. Need input on this

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Hello. We have 1 part we ran out of 7050-T7451 that did not take alodine after 12 minutes. We have had made several other parts out of this heat number and have had no problem, nor have any of us seen this.
We have reprocessed this part along with other parts from that heat and other heats as well. The others took.The part in question didn't. This was a three part run. The other two took.
We sent a piece of the suspect part to the mill who made it. They just responded, telling us that thier testing has proved it is, indeed, 7050-T7451 per AMS 4050.
Has anyone else ran across anything like this?

Erin Wright
machine shop / airplane manufacturer - Sandpoint, Idaho, USA