The advice in this thread is funny. You can't just ask someone out when you have never spoken to them before (corporate environment). That would come off as downright creepy, especially for gay dating. Take an indirect approach first. If he has friends in the department, see if those friends are easier to speak with. That way, you might get introduced to him through somebody else. If he's a loner, try approaching him with a question related to work. Expect what his answer would be and extend the discussion accordingly.
Don't sound dumb or annoying. You should be good at asking questions. See if you get a friendly response and start going a bit off-topic from there. Once you are introduced and have chatted for days, then it may be the good time to ask for drink/lunch. If you want to take a shortcut, bump into him on work lunch break. Haha. Don't spill the beans that you're gay soon after you become friends. Get to know him better and don't rush anything. Who knows, his personality might not be your type at all and then you wouldn't have to take it any further.