PSI - Issue 71

Ritik K. Nakhate et al. / Procedia Structural Integrity 71 (2025) 357–363

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et al., 2019) for Coating 1, Coating 2 and Coating 3 was found to be approximately 90 %, 84% and 75%, respectively.

Fig. 2. SEM images displaying (a-c) top as-sprayed surfaces and (d-f) cross-sectional surfaces of the coatings.

Fig. 3 . XRD patterns of different coatings show differences in their crystallization.

3.3. Electrochemical behavior A potentiodynamic polarization test in a 3.5% NaCl solution was conducted to evaluate the coatings' corrosion behavior with the polarization curves illustrated in Fig. 4. The results obtained from this study mentioned in Table 2 reveal that increasing plasma power from 25 kW to 30 kW reduced the corrosion current density of coating from 13.4 μA/cm² to 9.7 μA/cm², while further raising the power to 35 kW caused these densities to rise again to 16.1 μA/cm². Coating 2 showing the highest passive corrosion potential (−485 mV) and the lowest density (9.7 μA/cm²), demonstrating superior localized corrosion resistance compared to the others. The results indicate that the corrosion resistance is significantly influenced by the coatings' microstructure and phase composition, with minor compositional differences due to the use of the same feedstock powder, emphasizing the relevance of porosity and crystalline phase content, while factors like thickness and plasma power affect the corrosion current density in complex ways (Nayak et al., 2020; Yang et al. 2012). The EIS analysis results correlate with the previously mentioned potentiodynamic polarization findings regarding the passivation behavior of the coated samples, where the Nyquist plot reveals the largest diameter of these semicircles (Fig. 5a), indicates better corrosion resistance with the highest passivating film resistance (Kumar et al., 2020). The Bode magnitude plot shows a greater impedance value at low frequency for Coating 2 (Fig. 5b), and broader along with higher Bode phase angle of 48.9º (Fig. 5c) also indicating better chemical