Control of wetting angle of water on solid surfaces is of significant importance in applications where the surface is exposed to humidity, water or ice. Hydrophobic surfaces have attracted a lot of attention in recent years to reduce corrosion, wear and freezing of solid surfaces. One way of creating hydrophobic surfaces is to coat them with certain hydrophobic coatings. However, the main challenge is poor stability and cohesion of the coating to the surface during service. To investigate the effects of such microstructural features of pure aluminum as grain texture and morphology, exposure to air and surface preparation method on its wetting angle with water, a directionally solidified aluminum billet was cast and three cross sections in longitudinal, transversal and 45? directions were cut. The preferential orientations of the longitudinal, transverse and 45? cross-sections were determined to be (200), (200) and (111), respectively. Each section was separately etched and its wetting angle and roughness on selected positions of the surface were measures right after etching and after one, two, seven and fifteen days of air exposure. The studied positions included inside a grain as well as on areas containing a single grain boundary, triple boundaries intersect and multiple boundaries. Morphology of the selected locations was investigated on the day of etching and after seven and fifteen days following the etching by scanning electron microscopy. In order to study the effects of surface preparation method, all the steps were also carried out on the longitudinal cross section with (200) texture after polishing and etching. The results showed that the etching induced corrosion in a strong Cl bearing solution resulted in formation of deep, multi-layered and angular tunnels on the planes with (200) texture. On the planes with (111) texture, however, wide shallow cubes of lower surface roughness were formed. It was concluded that the surface texture at a given surface composition could affect the etching induced surface morphology and roughness. Wetting behavior of all the selected areas on all the etched surfaces was changed from hydrophilic to hydrophobic after one or two days of air exposure. Wetting angle of the inside grain area on the longitudinal cross section, for example, increased from 18? to 100?. This seemed to be due to adsorption of organic [I1] compounds on the surfaces. Increasing rate of the contact angle was gradually decreased by saturation of the surfaces of the organic compounds, and became steady after 15 days on all the cross-sections. The results suggested that the rate of adsorption and the amount of adsorbed organic compounds by the oxide layer on the (200) texture was more than that of the surface with (111) texture. The results also suggested that wetting of the selected locations on the three cross sections followed Cassie-Baxter model. It was found that the surface crystalline texture , surface morphology, the state of crystallinity of the surface aluminum oxide layer , air exposure and presence of such particles as SiO 2 particles affected the wetting angle of aluminum with water. [I1] ارگانيک يا ميکرو ارگانيزم ها؟