The two older methods of polished brass coatings were just that, a coating. If your faucet was to get a nick in the coating then water would get underneath the finish and tarnish it. Most of the time this would happen at the end of the spout where the threads are. Another common location to have a faucet tarnish is at the bottom of the sink at the pop-up assembly. The pop-up assembly comes into contact with water more than any other part of the faucet. This therefore has an even greater chance of tarnishing. So what can you do about it? … With your old faucet nothing. But now Kohler, Grohe, Moen and Delta have a lifetime finish. Kohler calls it Vibrant. Grohe calls in The Infinity Finish. These finishes are guaranteed not to tarnish. They use a new technology call PVD (Physical Vapor Deposition). This is the same technology that they have used for years on car emblems. Up until now it was too expensive to use on faucets. The faucet is made in chrome and placed in a room that is filled with ionized gases and is charged to facilitate molecular adhesion. The faucet is then removed and its finish is about 10 times harder than that of chrome and is guaranteed not to tarnish.