2.2. Preparation of Steel Substrates

Structural, low carbon steel (P265GH) and austenitic, stainless steel (316L) were used as substrates. The chemical compositions of steels are shown in Table 2 (according to PN/EN 10027-2 and EN 10273). Before coating application, the surface of P265GH steel samples was sanded with sandpaper (grade 800) (R_a = 137 ± 14 nm after sanding, according to the PN-ISO 4288 standard with 20 measurement points per an individual sample, 0.8 mm length of measurement section, Olympus, LEXT OLS4000, Tokyo, Japan), cleaned in detergent and distilled water, and then etched in sulfuric acid (12%). After that, P265GH substrates were cleaned in distilled water and ethanol and left to dry at room temperature (20.5–21.5 °C). After sanding, the 316L steel samples (R_a = 194 ± 9 nm, according to the PN-ISO 4288 standard with 20 measurement points per an individual sample, 0.8 mm length of measurement section, Olympus, LEXT OLS4000) were rinsed in distilled water and etched in hydrochloric acid (9%), then rinsed with distilled water and ethanol and left to dry in room temperature (20.5–21.5 °C). The 316L steel surface was not sanded (assuming that coating would be deposited on an existing installation system in which an ideally treated surface was not possible).

Chemical compositions (%) of P265GH and 316L steel.