On July 1, 2018, Canada will impose countermeasures in the form of surtaxes against C$16.6 billion in imports of steel, aluminum, and other products from the U.S., representing the value of 2017 Canadian exports affected by the U.S. tariffs on imports of certain steel (25%) and aluminum (10%) products from Canada.

Surtaxes of 25% will apply to certain US steel products. Surtaxes of 10% will apply to certain US aluminum and other products. The lists of affected products can be found here:

https://www.fin.gc.ca/access/tt-it/cacsap-cmpcaa-1-eng.asp