You will need to optimize your process based on the alloy mixture, pH and such, but 0.5A/dm2 is typical for white bronze plating and should be a good starting point.

thank you very much  Ron Reiserer for the answer.

I agree with Ron. You will need to optimize your process and that may be easier to do with controlled potential than current. Then you can determine the suitable current from this optimization.

You will also need to consider the carbon electrode. Most carbon materials do not have sufficient cathodic overpotentials for depositions and their performance may be marred by hydrogen evolution.