First, pine is a very poor outdoor wood. It easily rots when it gets wet. There are other woods that would have been better choices.
Second, no finish lasts long when it is continually exposed to sunlight and other outdoor conditions. The more clear the finish, the quicker the finish will deteriorate. Even with the best true marine clear finishes, the best you can expect is about a year at which time the finish will need to be sanded and a couple of new coats applied. Stay away from any of the Big Box exterior "spar" poly varnishes. Any finish containing polyurethane is quickly attacked by the UV in sunlight. It quickly gets cloudy and loses adhesion and then chips off.
The more opaque the finish, the longer it will last. Therefore, a good exterior oil based paint is the longest lasting finish you could use. Good paints can last 3-5 years in many cases.
The bottoms of the legs are the most prone to water absorption and therefore, the part that rots first. The best plan is to thin your finish one part finish to four parts mineral spirits. Pour it into a container that the leg will fit into. Let the leg sit in the liquid for 24 hours. Then prop it up so the leg can dry for 48 hours. Once you have all the legs treated, you can begin applying your clear of colored coat.
Adding to what he said, look at adding feet to the legs. Something to keep the end grain wood off the ground.
Even nailing on some edge grained wood like cedar, ipe, mahogonay or teak.
Also, an old time wood treatement is 50/50 turpentine/BLO blend is pretty good. Apply this and let it dry for maybe a week or longer. Then paint. You could also soak the legs in this mix.
Jim
__________________
If I were a frog and my friends were in a pot of boiling water I would be of better use if I stayed on the outside and turned the heat off.
The May/June 2009 issue of FWW (No. 205) did a review of different finishes and concluded that penetrating oil finishes were essentially worthless, water-based finishes and spar varnish finishes not much better. They found 2 that worked quite well after one year, both made by epifanes (www.epifanes.com) But one required 7 coats! And it ain't cheap. ( I haven't tried epifanes and prolly won't but just to let you know it's out there.)
As others have said, pine's not your best choice for outdoor applications. You might try coating exposed grain with Titebond III waterproof glue. And recoat periodically. My parents used a colored stain on their deck three years ago and it still looks quite good. So if you don't care about showing the wood's grain, might go with a stain rather than paint. Paint cracks and peels and is difficult to renew. Stain is easier to refresh.
Geodesic Shop Crawl April 10th 
06-03-2009, 11:26 AM
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