We bought a bronze finished lockset about five years ago, and now a lot of it is ashy looking and green in some places. It looks a little worse every year. It's on an exterior door facing west. Would it be the sun causing such discoloration? If so, what's a good finish for an exterior door lockset?
It's called a tarnish or patina and is caused by oxidation of the copper in the bronze. The sun's heat will accelerate that reaction somewhat compared to one in a cooler place.
If you don't like it, simply clean the lockset with Brasso when it starts to look discolored. It will take some elbow grease the first time because the tarnish has had time to build up, but if you keep up with it, subsequent times will be a lot easier.