Bad adhesion of chromate passivation on cyanide zinc

Q. hi everyone I work in a factory in Iran we have pure zinc and zinc-nickel lines. our OPC in galvanic line is as following:
degreasing ---rinse---acid dipping---rinse---electroplating pure zinc----nitric acid with PH=1----yellow passivation----rinse
but we recently have problem
1: bad adhesion chromate layer so the layer peels easily
2: sometimes there are blisters on the surface
meanwhile we have non-cyanide bath
thanks for your helping

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A. Hi,
Probably you are overdosing the brighteners. both your problems are related to this.
200 grms (for every 1000 ltrs bath) activated carbon packed in the filter and run for three hours will help. do not forget to clean up the filter immediately after this before re use the filter.
To free from blisters, use the same technique once in a week or once in ten days.
Hope to hear the good news.
Regards