Don't even think about it. You'll ruin the deck and turn it into a skating rink when it's wet. I happen to love Cetol Natural Teak and we use it for grab-rails, our traveler horse, the trim around the companionway, drop-boards, et al
but never, ever, on a deck. It will eventually need to be stripped off and in so doing the caulking between the planks will be ruined. A neighbor of ours ignored these warnings a few years ago and now profoundly regrets it. His best quote for replacing his teak is upwards of $50G (USD). If you can't stand the "gray", you can use:
We use this aboard our boat and we are very frequently complimented on our teak decking (in our cockpit). It is not inexpensive, however, and, it does have to be redone at roughly 4-6 month intervals, but doing so is not difficult, just time consuming.