10 or a few more years ago, a research paper on the topic of wood preservatives and bee hives, was published (I don't remember where, can anyone help?). Perhaps there is more concern now, but as I recall, the conclusion was that once well dried, most of the preservatives were suitable for bottom board use. Paint on top of the preserved wood would be an added level of separation of the chemical from the bees. As indicated by the other messages, a high level of caution in this use is justified. I don't think use of this type of preservatives on any of the other interior surfaces of the hive is advisable. You might consider some other methods like dipping in melted wax, which are inherantly safer for the honey.