electric hot water heater

My 40 gal water heater is about 8 years old. After installing a new white tub I now notice that the hot water is brown. I drained the tank. The pipes seem to produce clear hot water, but as soon as the water is left to sit for a few hours its back to brown again. Can this tank be decorroded? If not what is a quality tank that will give me good service, relatively trouble-free? Many thanks.