Could merchant conversions deter piracy?

What ships could become armed merchant cruisers today, and how useful would they be against piracy?

A small container ship could serve as a visible armed presence intended to deter attack.

Passenger liners are identified as a historical source of armed merchant cruisers. For a modern equivalent, a small container ship is suggested. Its role would chiefly be visible armed presence, discouraging pirates from attacking it. This is a brief proposal, with no detailed armament or operating scheme.