Metal finishing Q&As since 1989
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Zinc dichromate hydrogen embrittlement
We are a job shop in Gimli, Canada. We just received an order to plate some pins. These are spec to Type II yellow dichromate, which we do. The drawing also specs must be free of hydrogen embrittlement. The material is 1.00 in. dia. stress proof. No other spec is stated. No Rockwell rating is specified. We plated and them baked as per embrittlement procedures. 400 degrees for three hours. After they cooled we took a few and hand dipped at various times, but the yellow would not stick. We tried some quick dips in the nitric to reactivate, but the pin just turned black and still would not take the yellow.
Any help or suggestions would be greatly appreciated. Does stress relief material not require baking?
Thank you for any assistance.
Shop owner - Manitoba, Canada
May 9, 2010
Dear Greg Agnew,
no standard is recommending 400 °C for three hours.
Better refer ISO 9588 or ASTM B850-98.
Based on the Tensile strength fix the treatment hours.
you will never get the same finish compare with the regular parts
(without hydrogen de-embrittlement)
- Salem, Tamil Nadu, India
May 12, 2010
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