OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 A quantitative assessment of the corrosion resistance can be obtained by calculating the polarization resistance using equation (1) from the polarization curves. The value of Rp characterizes how resistant the specimen is to oxidation with respect to the applied potential. Based on the data obtained, it follows that the annealing the pre-deformed specimens contributes to an increase in the polarization resistance of specimens printed from silicon bronze. In turn, when printing specimens with the addition of aluminum filaments, the most effective in terms of increasing the polarization resistance is the addition of Al-5Si alloy. For a more detailed assessment of the effect of a corrosive medium on the surface of the specimens, it has been analyzed using a laser scanning microscope. After testing, a micro-topology pattern formed on the surface of the specimens, with clearly distinguishable individual structural elements (grains, annealing twins, etc.). Pitting marks on the surfaces of silicon bronze (Fig. 7) and bronzes printed with the addition of aluminum filament (Fig. 8) were not detected. The boundaries of grains and annealing twins did not undergo any significant dissolution. At the same time, the visually observed surface pattern is not the same in all cases. To quantify these differences, the surface roughness of the specimens under study was evaluated. From the data obtained, it can be seen that the specimens printed from bronze C65500 after testing (Fig. 9) are characterized by the most significant surface roughness. The use of high-temperature annealing contributed to the decrease in the arithmetic mean value of the asperity height (Ra) by 6–12 %. The smallest roughness is observed on the corroded surface of the pre-deformed and annealed specimen (Ra = 0.275 µm). The multiwire approach had its effect on the corroded surface roughness. Based upon the data obtained, the least surface roughness (Ra = 0.296 µm) is exhibited by the specimen printed with the addition of Al-5Si alloy. Based on the data obtained, it follows that the surfaces of the specimens with the lowest roughness are oxidized more uniformly, which may indicate its higher resistance to the electrolyte. Another quantitative characteristic of corrosion resistance of specimens is the loss of mass. To obtain it, the specimens were weighed on an analytical balance before and after testing. As a result, the mass loss was determined for all the studied specimens (Fig. 10). High-temperature annealing, as well as annealing the pre-deformed specimens caused the reduction in mass loss by 15–30% in comparison the that of as-printed silicon bronze specimens. The addition of aluminum filament made it possible to further reduce the weight loss of as-printed specimens by 13–31 % with regard to both as-printed and annealed specimens of bronze C65500. Ta b l e 2 Parameters of Taffel curves according to the data of potentiodynamic tests of specimens printed from C65500 and with the addition of aluminum filament Specimen designation Parameters of polarization curves Ecorr , mV Icorr , μA βa βc Rp, kOhm C65500 (1) –178 5.54 0.030371 –0.02667 1.7 C65500 (3) –210 5.74 0.067731 –0.05687 2.7 C65500 (7) –202 5.6 0.064345 –0.08164 2.4 C65500 (annealing) –229 5.71 0.069095 –0.10014 1.7 C65500 (deformation + annealing) –223 5.5 0.110449 –0.13455 4.8 C65500 (10 wt.% Al) –251 6.6 0.168932 –0.12941 3.6 C65500 (10 wt.% Al–5Si) –239 5.2 0.246156 –0.18557 6.3 C65500 (10 wt.% Al–12Si) –193 8.4 0.116204 –0.13008 5.6
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