[John Smith_]

Welcome to the forum.
What you are asking is not possible to answer. Proceed at your own risk.
If you need timber for your tank, I would suggest you purchase plastic ones from the store or online aquarium supply site.
Edit: or, if you really love it, and really want to use it, put it in a large tank of fresh water and change the water daily to allow any possible contaminates to leach out.(even boil it in fresh water, if you like).
and again, there are NO guarantees along any lines - proceed at your own risk.

 

[John Smith_]

when I think of "driftwood" I think of wood floating around the ocean (rivers or lakes) for long periods of time and weathered nicely. BUT - contaminants such as oil, gasoline, and other terrible chemicals that also float get obsorbed into the wood. So, when using "driftwood" in a residential setting, I would take the same precautions as used "pallet wood" as we never know for sure what that wood had been exposed to over the years and how it could affect our health or the health of our pets. (dogs, cats, birds, fish, etc). So with that, I think that we all suggest NOT to use any wood in a fish tank with small fish that have very delicate health concerns.
we would like to see your aquarium, though - many of us here have fish tanks in one form or another. My brother has a 300 gallon saltwater Rock Aquarium that he takes great care in not contaminating it with outside material.