Thank you for yours answers.
I think that my questions haven't been completely understood.
I think we can resume the pink-ring's process in 2 steps:

Step 1.- During drilling, there is a separation between the resin and de
copper around the hole.

Step 2.- In the electroless copper and galvanic  lines,  acids attack the
black oxide and give pink-ring as result.

The peel strength for the reduced BO is lower than the 'normal' black oxide,
then is hard to understand how it can help in step 1.

OK, the layer of reduced copper protects the oxide from the acid's attack,
but in the  electroless  copper and in the galvanic lines there are
chemicals   that attack  the copper  (0), for example,  sulphuric/hidrogen
peroxide and   NPS. Then, how can DMAB help in step 2? 

What is the reason of all these questions?

Well, is difficult to be comfortable with a process that is not well
understood, and I need to  be sure of the black oxide's quality before pressing.

thanks

Toni