Hi Denis Petrov,

               I came across a similar situtation before and yes, Au
was not electroplated on to the Aluminum substrate... in my
experiment, a sulfite based Au plating solution was used, and even
after 1 hour,   au was not plated on al substrate... i guess it may be
becos of adhesion related issues, since Au was getting plated on Cr
substrate (however, surafce quality of plated gold on Cr substrate was
poor).... interested to know the exact reason, if anyone can explain..

Regards,
A. Ravi Shankar,
Senior Research Scholar,
Microelectronics and MEMS Lab,
Electronics & ECE Department,
IIT Kharagpur.