Originally Posted by mariusgmioc
Cleaning a rusted damascened piece is a very tricky task.
For very little rust over gold koftgari, I used Picreator's Metal Decorroder, then gently wiped off the rust. I managed to leave most of the koftgari in place but there were some losses.
For a more heavily corroded piece, it might be a completely diferent story and I would like to know the answer myself.
Your method is perfectly safe when the underlying crosshatched iron surface is uncorroded and there is a direct bond. Where you tend to get losses is when rust goes under the overlay metal. But the decoration is eventually doomed in such case because as the corrosion advances it will flake anyway. For the heavier corrosion you mention, I carefully use dental picks of various shapes, plus small horsehair brushes, to remove the rust BETWEEN the elements of the design (i.e. where the iron was exposed to begin with), working around the precious metal. Of course when the rust has spread under the overlaid design, the adhesion is poor and there is the real risk of loss. You just avoid hitting the deco, and hope for the best.
Note that gold koftgari tends to be more stable than silver. This is because gold does not oxidize or tarnish. Silver will, and moisture seeping underneath from adjoining rusting of the iron will accelerate the tarnishing and hasten the deterioration of the bond.