[Method 1]

In the following solution at 50 ° C for 10 min:

Potassium dichromate saturated solution 0.35 sulfuric acid (d = 1.84) 10

And then brush to the charcoal residue, washed with distilled water, 70 ° C under dry. This method is suitable for requests to reach the maximum peel strength of the place.

[Option 2]

In the lead tank, the sulfuric acid concentration of 500g / l, anodizing 90s, voltage 6V, rinse with water, distilled water, 70 ° C dry, adhesive pieces for the anode, after treatment 5-10% chromium oxide solution Passivation for 20 min.

[Method 3]

In the following solution at 85-90 ° C for 10min:

Oxalic acid 37 sulfuric acid (d = 1.84) 36 water 300

Washed with distilled water, with warm air dry.