If the driftwood comes from a river, it is pretty likely that it will already be waterlogged (will sink straight away when you put it into your tank) and will already have leached out most of its tannins. I would scrub it to remove any external scum, soak it in hot water to sterilise it for a couple of days, then it should be ready to add to your tank. It could turn your tank water a murky brown colour, this is just tannic and humic acids which won't harm your fish, but using activated carbon or Purigen will help to remove the colour.