Optimization of process parameters with experimental design methods in the application of superhydrophobic coatings on aluminum surfaces

Surface coating processes are a subject that is used and developed extensively to give the desired surface properties to the materials. In this study, it was aimed to develop superhydrophobic coatings on aluminum surfaces with the dip coating method, and the experimental conditions were also optimized with the Taguchi experimental design method, which is one of the experimental design methods. In experimental design; 3 factors were determined as sanding, etching and modification, and 3 levels were determined for these 3 factors, and their degree of influence and interactions with each other were examined. Aluminum plates with dimensions of 7 cm x 2 cm x 1.5 mm were used as samples in the experimental studies. 3 different sandpapers (400, 600 and 800) were used in the sanding process of the samples. Etching and modification processes were carried out with 2 different experimental studies. In both studies, 9 different experiments were carried out in L9 orthogonal arrangement using Minitab 18 program. In the first experimental study; the sandede samples, were immersed in 4 M hydrochloric acid (HCl) solution for 2, 4 and 6 minutes and etched. For the modification, the etched surfaces were immersed in an ethanolic solution of dodecyltriethoxysilane at a concentration of 0.01 M for 8, 16 and 24 hours. In the second series of experimental studies; etching processes were carried out sequentially with base + acid treatment. Here, sanded samples were etched by 1 M sodium hydroxide (NaOH) solution for 10 minutes. Then, a second etching was carried out by immersing it in a solution of 20 ml distilled water (H2O): 8 ml HCl: 1 ml (acetic acid) CH3COOH for 3, 5 and 10 minutes. In the modification process, the etched samples were immersed in an ethanolic solution of 2 % by mass of palmitic acid for 15, 30 and 60 minutes. The superhydrophobic properties of the surfaces were determined with the contact angle measuring device and the surface morphologies were examined by Scanning Electron Microscope (SEM). According to the contact angle results; in both studies, contact angles of over 150° were obtained and aluminum surfaces were determined as superhydrophobic. In SEM images; the rough superhydrophobic surfaces were observed. According to the results; it has been determined that the applied method can be used in the development of superhydrophobic coatings on aluminum surfaces.