Tin plating is normally done to impart solderability to a variety of base metal substrates. It is a silvery, blue-white metal that is ductile, solderable, and covers very well. The solderability of tin can be affected by the substrate, since several metals (including brass and zinc) tend to react with and migrate into the tin forming relatively non-solderable intermetallic layers. Zinc will migrate into the tin and severely limit the shelf life of the finished parts. This migration can be mitigated by the common practice of applying an undercoat of copper or nickel, or a combination of copper with a flash of nickel through which the zinc cannot migrate. Tin has a typical thickness of .0011”. In general, matte tin has better solderability but bright tin is specified more because of its appearance. Tin does not tarnish easily, making it a good choice as a decorative finish.