Anodizing current density problem

Hello everyone,
I would like ask for advice with anodizing.
I try to anodize 5082 aluminium just for hardened surface, not for dye, just for natural look.
I have two lab power supplies, first 0-3A 0-30V, second 0-10A 0-30V, a little tank with 20% sulfur acid 1,5L, anode object surface is 76cm2,
katode is 3x larger than anode (around 228cm2).
From calculation I need current density 10V but with my power supplies I cannot go over 8V and over time (80min) it goes to 7V. I tried as katode lead and aluminium,
both with same results. How could I achieve correct current density ? Do I need different power supply with more voltage range ?
Is it possible to somehow connect both these power supplies to achieve more voltages 0-60V ?

thanks