PSI - Issue 16

Barbara Nasiłowska et al. / Procedia Structural Integrity 16 (2019) 230 – 236 Barbara Nasiłowska et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. The GO deposition process: (a) application, (b) spinning, (c) vacuum drying.

Surface of steel S235 and glass was cleaned by argon plasma (power = 100W) for 1h. The samples were placed in the vacuum handle of the rotary head and GO was applied on the surface (Fig. 2a) and subjected to centrifugal force (Fig. 2b). The last stage of preparation was vacuum drying in 320K for 48 h (Fig. 2c).

2.2. Structural analysis and roughness measurement

The surface analysis was made with use of confocal microscope LSM 800 Zeiss. It is a confocal laser scanning microscope that uses laser light in a confocal beam path to capture defined optical sections of the sample and combine them in a three-dimensional image stack. Additionally surface morphology was made with use scanning electron microscope Quanta FEG 250.

2.3. The static sessile drop method

The sessile drop contact angle is measured by using an optical subsystem to capture the profile of a pure liquid on a solid substrate. The angle formed between the liquid – solid interface and the liquid – vapor interface is the contact angle. For each sample 16 photos were made (8 form left side and 8 from right side) for droplets deposited on steel and glass surfaces. Based on the photos the angle formed between the liquid – solid interface was measured and presented with standard deviation. water acrylic resin water acrylic resin water acrylic resin GO glass water acrylic resin

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GO glass GO glass steel

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Fig 3. Schemes of designed surfaces for wettability measurements: (a) glass, (b) glass with GO film, (c) steel S235, (d) steel S235 with GO film, (e) steel S235 with initiated surface corrosion. corrosion

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The volume of the single water drop was 5 µl and acrylic resin was 7- 8 µl. Due to acrylic density it was not possible to obtain the smaller drop which could automatically disconnect form the needle of the syringe. The distance between needle and the surface was not bigger than 5 mm since higher distance could result in spattering of