Duplex stainless steels (DSSs) are widely used due to their corrosion resistance. Austenite and ferrite determine the excellent properties. Ferrite provides strength and good corrosion resistance, while austenite provides toughness and weldability. During our research, samples were produced with ER 2209 duplex steel wire using wire arc additive manufacturing (WAAM). Two different 17 V and 19 V arc voltages were used during the production. Two shielding gases were used for each voltage: M12-ArC-2.5 and M12-ArHeC-20/2. The research aimed to determine the ferrite ratio as a function of the welding parameters. The ferrite (or austenite) content must be between 30% and 70% for duplex stainless steel welds, according to the ISO 17781 standard. Based on our research, it can be stated that the austenite ratio increases as the voltage increases, thus failing to fulfill the standard's requirements. The helium content reduced the ferrite ratio even when the 17 V voltage was used due to the gas's higher ionization potential. During the metallographic examination, our welded samples met the standard requirements for the austenite content for 17 V arc voltage and M12-ArC-2.5 shielding gas. The ferrite content in the entire sample cross-section fell between 30-42% during feritscope and image analysis measurements. These welding parameters can be recommended for industrial applications.

Hydrophobic coatings from chitosan–surfactant composites (ca. 400 nm thick by UV-Vis spectroscopy) for possible corrosion protection were developed on glass and zinc substrates. The surfactants (sodium dodecyl sulfate, SDS or sodium dodecylbenzenesulfonate, and SDBS) were added to the chitosan by two methods: mixing the surfactants with the aqueous chitosan solutions before film deposition or impregnating the deposited chitosan films with surfactants from their aqueous solutions. For the mixed coatings, it was found that the lower surface tension of solutions (40–45 mN/m) corresponded to more hydrophobic (80–90°) coatings in every case. The hydrophobicity of the impregnated coatings was especially significant (88° for SDS and 100° for SDBS). Atomic force microscopy studies revealed a slight increase in roughness (max 1.005) for the most hydrophobic coatings. The accumulation of surfactants in the layer was only significant (0.8–1.0 sulfur atomic %) in the impregnated samples according to X-ray photoelectron spectroscopy. Polarization and electron impedance spectroscopy tests confirmed better barrier properties for these samples (40–50% pseudo-porosity instead of 94%). The degree of swelling in a water vapor atmosphere was significantly lower in the case of the impregnated coatings (ca. 25%) than that of the native ones (ca. 75%), measured by spectroscopic ellipsometry. Accordingly, good barrier layer properties require advantageous bulk properties in addition to surface hydrophobicity.