I've had good results with Penofin. They no longer sell it at Home Depot but I was able to get it at a paint store. My friend uses it on their deck at there mountain cabin that gets 10-12 feet of snow on it every year and it holds up. It's expensive at about $50 per gallon.
Below is a fence I recently built that was sealed with Penofin - I used Transparent Redwood. The fence is made of redwood other than the treated posts.
