commercial metals have recently been reconsidered as useful materials for functionalized surfaces with controlled wettability of a stainless steel surface exhibits a time-dependent transition initially from a hydrophilic state to a relatively hydrophodic state.The static contact angle of a
water droplet was monitored on polished stainless steel surface severy 24h, and a rapid increase in the contact angle, from 44° to 81°, was found during the first three days. The contact angle reached 98° in 40 days. To clarify the main factor causing the phenomenon, we compared the contact angles of water stored in four different environments for five days, where the oxygen and moisture levels were con-trolled.From the
difference in contact angles depending on the amount of oxygen,we reached the conclusion that oxygen is likely the main cause of the aforementioned phenomenon.Finally,we de-monstrated time-dependent wettability on a micro-grooved stainless steel surface whose initial super-
hydrophilicity became superhydrophobic after 30 days.