Hydrogen embrittlement testing

How often should one do hydrogen embrittlement testing. We have Chrome, nickel, and electroless nickel. Any help would be appreciated thank you. I have read through the Specs but they don't seem to give me a clear answer.

Steve, the frequency will depend on whether you must meet a specific standard or just a customer requirement. For example, we must perform this test monthly on our zinc and manganese phosphate processes. Our test consists of plating 4 test bars (supplied by the lab) and submitting them for testing. The tests may take up to a week and run us an average of $75.00 per lot.

Typically in the industry, four notched test specimens per tank are required. Good luck.