## 3 Results and Discussion
### Electrochemical Assessment
#### 3.2.2 PPC Evaluation  
Both samples presented a similar PPC curve shape (Figure 4). The curve was tilted in the cathodic branch, meaning an activation control [16]. The curve in the anodic branch showed different shapes according to the potential. The curve was vertical at low voltage, indicating a passive control. The 316L SS possesses a passive film that results in chemical inactivity of the sample [16]. The breaking passive film potential was higher for the LPBF samples (1.023 V vs. Ag/AgCl 3 M KCl) than that for the wrought sheet samples (0.582 V vs. Ag/AgCl 3 M KCl). The higher thermodynamic stability of the LPBF sample's passive film is due to the larger size of its grains [7]. This decreases the cathodic effect of the grain boundary on the grain. The molybdenum accumulates at the grain boundary. The molybdenum, being nobler than iron, contributes to the cathodic effect of the grain boundary on the grain [17; 18; 1; 2]. Another difference in the PPC of the samples was the presence of fluctuations in the anodic branch of the wrought sheet sample. Metastable pitting is responsible for these fluctuations [7]. The reduction of the grain boundary cathodic effect mitigates the metastable pitting formations [13]. The corrosion potential of the wrought sheet sample (\(-0.174\) V vs. Ag/AgCl 3 M KCl) was lower than that of the LPBF samples (\(-0.063\) V vs. Ag/AgCl 3 M KCl). Note that the polarisation curve transitions from the cathodic branch to the anodic branch at the corrosion potential. In the other words, the corrosion potential is defined by the potential at which the cathodic and anodic branches intersect. The grain size is also responsible for the more noble LPBF samples. The spontaneous repassivation of the samples was not possible for both types of 316L SS, as indicated by the absence of an inflexion point in the return curve. It is noted that these results coincided with AEN data, validating the electrochemical results.  
Table 2 lists the corrosion features of the samples obtained with PPC. The passive film corrosion rate (\(C.R._{pass}\)) was slower for the LPBF samples than that for the wrought samples. The polarisation resistance (\(R_{p}\)) of the wrought sheet sample was lower than the LPBF sample \(R_{p}\). This factor (\(R_{p}\)) is proportional to the corrosion resistance. These results showed  
Figure 4: PPC of the samples in 0.6 M NaCl.  
that the corrosion resistance of the LPBF sample was higher than that of the wrought sheet samples. \(C.R._{pass}\) and \(R_{p}\) were calculated with Equation (3) [19] and (4) [20], correlatively.  
\[C.R._{pass}=\frac{I_{pass}\times M}{F\times n\times\rho} \tag{3}\]  
\[R_{p}=\frac{\beta_{c}\times\beta_{a}}{2.303\times I_{corr}\times(\beta_{c}+ \beta_{a})} \tag{4}\]  
Here, \(I_{pass}\) is the passive film current density, \(M\) is the molar mass of the iron (55.88 g/mol), \(F\) is [PERSON]'s constant (96,500 C/mol), \(n\) is the electron transferred (3 e\({}^{-}\)), \(\rho\) is the density of the iron (7.875 g/cm\({}^{3}\)), \(I_{corr}\) is the corrosion current density, and \(\beta_{c}\) and \(\beta_{a}\) are the cathodic and anodic slopes. \(I_{pass}\) was measured in the vertical curve of the anodic branch. \(I_{corr}\) was calculated with [PERSON]'s lines intersection method [21; 22]. The corrosion rate in the equilibrium (\(C.R._{corr}\)) was higher for the LPBF samples than for the wrought sheet samples. However, this parameter is not of much importance in the corrosion kinetics of the passive film owing to this being defined by \(C.R._{pass}\). The degradation rate of the material in the corrosive process is defined by this parameter for passive material [23]. \(C.R._{corr}\) was estimated using Equation (5) [19].  
\[C.R._{corr}=\frac{I_{corr}\times M}{F\times n\times\rho} \tag{5}\]