American National Standard for Electrical Metallic Tubing—Steel (EMT-S)
This Standard covers the requirements for steel electrical metallic tubing, for use as a raceway for wires or cables of an electrical system. Finished tubing is typically furnished in nominal 10-ft (3.05-m) lengths. It is protected on the exterior surface with a metallic zinc coating or alternate corrosion protection coating (see UL 797 for alternate corrosion protection coating requirements) and on the interior surface with a zinc or organic coating.
ANSI C80.5-2015: American National Standard for Electrical Rigid Metal Conduit—Aluminum (ERMC-A)