Contact angle and rivulet width hysteresis on metallic surfaces. Part II: With cooled surface

The results of contact angle and width of the rivulets measurements on plain surfaces made of aluminium, brass and copper are presented in the paper. The measurements were done for the rise, decreasing and again increasing of flow rate on the cooled plates. As a result the hysteresis of contact angle and rivulet width was revealed. It was also noticed that aluminium and brass at certain flow conditions can lose their hydrophobic properties and became the hydrophilic materials. The worst wetting properties were observed for copper. It is supposed that the more electrons on the last shell are the more hydrophilic metal is under flow conditions. Lower temperature improves the wetting properties of the metals and favours the disappearance of the oxide barriers on aluminium and zinc (brass is an alloy of zinc and copper). Since the contact angles on two rivulet edges differ, it is not justified to assume a segment of a circle as the rivulet cross section shape. (C) 2009 Elsevier Ltd. All rights reserved.