stainless steel is actually worse than galvanized steel.
we are trying to talk you out of using any
don't you get it?
granted, most LPS mount driftwood on slate with screws,
but most LPS are idiots who's advice we try to undo here.
realistically, if you fill your 90gal with a few large fish,
and low tech plants, such screws won't matter at all.
but if you go with small fish, and especially shrimp,
then sensitive high tech plants, you really don't want
any potential toxins and metals in your tank at all.
think of it another way. if the inhabitants of your tank
ever show signs of distress, and you are trying to
troubleshoot your environment to restore their good
health, the last thing you want to worry about are
the screws you used on your driftwood...