On the duration of the protective effectiveness of superhydrophobic coatings

The durability of superhydrophobic coatings obtained on St3 carbon steel by nanosecond laser texturing of the surface, ultraviolet radiation treatment in ozone plasma, and deposition of a fluoroxysilane film has been studied.The contact angle of wetting of the coating, on average, is 172°.After 112 days of exposure to 100% humidity, the samples with the superhydrophobic coating did not show signs of corrosion damage, retaining the original wetting angle.Studies conducted for 100 days in an atmosphere with 100% humidity and containing corrosion stimulants CO 2 , H 2 S, NH 3 in pairs and simultaneously all three in the maximum permissible concentrations typical for livestock buildings showed a decrease in the contact angle to 167-162° in the absence of signs of corrosion damage.After the tests, the samples were kept for 19 months in desiccators in a chemical laboratory, after which the contact angle on the superhydrophobic surface was 167-168°.Further, with these samples, corrosion tests were carried out in the gas and liquid phases of solutions with 50 g/L NaCl or NACE (5 g/L NaCl+0.25 g/L CH 3 COOH), saturated with CO 2 up to 1 excess atmosphere, or solutions of SO 2 (1 and 3 wt.%).After testing in the gas phase, the coatings retained superhydrophobicity, and after the liquid phasehydrophobicity with contact angles of the order of 130-140° after testing with SO 2 and about 100° after testing with CO 2 .Subsequent exposure of the samples to air for 2 weeks led to a sharp increase in the contact angles.