Flaking of chromate on zinc plated crimped ferrules

Q. We have a product that is a ferrule 1.947" -1.927" long .065 - .058 Thick and 2.445" - 2.420" dia. They are zinc plated to a minimum of .003 thickness with dichromate coating over entire part. We have noticed of late that the dichromate finish flakes of when crimping we have not had this problem for well over ten years but has started again. Do you have any suggestion as to why this might be happening. We have noticed that the bright ones flake and the dull one do not. Could it be to much brightener in the dichromate.

If that's your observation, you are dead right; however, if it's the zinc peeling off then it's too much brightener in the plating tank, not the dichromate.

If it's the dichromate peeling off and not the base zinc metal then it's the residual film of the brightener on the parts that has not been neutralized by an ineffective dichromate process.