What is the most inhospitable environment for metallic structures you ask? Well, a sea port would be a good guess. The combination of moisture, oxygen and salt damages metal worse than rust does. Saltwater corrodes metal five times faster than fresh water does and the salty, humid ocean air causes metal to corrode 10 times faster than air with normal humidity.
So, would an ordinary signmaker accept the challenge of making a steel sign for a marina in an area that is plagued by gale-force western winds in the winter months? Probably not. But then again, Kouros is not an ordinary signmaker.