On new installations of ductile iron pipe, it is good, cheap insurance to protect your project with polyethylene encasements. Polywrap is an easy-to-install sleeve that is pulled over the pipe at time of installation. This is the most economical as well as effective way to protect ductile iron pipe from exterior corrosion. There are many types of polywrap; 8MIL linear low density is the most common. While it is typically black, colors are available to mark what the pipe is being used for.
AA Thread Seal Tape