Bleach would absorb into the wood and leach out, but there is a way around it. I love using wood from the beach because it already come leached of its natural tannis as well as completely debarked and debrided into awsome shapes. Any salt that is on the wood is usually just encrusted on the surface, so a good soaking pre-tank will get rid of it.
The procedure I used was to soak my collected driftwood in a 10 gallon plasitc garbage pail of a 10% bleach solution overnight. Then I rinsed it off and put in clean water with a libral amount of tank dechlorinator added. I soaked it like that for a week, doing daily water changes. Then I gave it a final rinse and put it right in the tank. The wood is still there, two years later, although I really need to get some more, my clown plecos have knawed it to nearly nothing.
~~Colesea