## 3 Results
### Analysis of Chemical Corrosion by Linear and Cyclic Voltammetry
It was observed that the unaltered 2.5% CMC achieved generalized corrosion on the steel sample, which was desirable because it occurred over a long time and the entire surface was affected and, therefore, visible. After the corrosion analysis, the steel samples were analyzed from a microstructural and chemical perspective. From the structural analysis, shown in Figure 8, for the sample of improvement of steel corroded in fresh CMC 2.5%, pitting was observed, much less than for the sample corroded in CMC 50. The greater amount of pitting on the sample corroded in CMC 50 provided premises for a faster appearance of cracks on the surface. Also, it can be seen from Figure 8c,d that deposits of the conglomerate type were distributed both on the surface and inside the pitting. These were due to the presence of particles in the suspension attributed to residues from previous tempering cycles. Table 5 shows the chemical analysis of surface affected by corrosion in three different areas. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & \(\mathbf{E_{0}}\) **(mV)** & **ba** & **bc** & **Rp** & **Jcor** & **Vcor** \\  & **(mV)** & **(mV)** & **(ohm\(\cdot\)cm\({}^{2}\))** & **(\(\mu\)AA/cm\({}^{2}\))** & **(mm/an)** \\ \hline CMC & \(-1028.5\) & \(773.2\) & \(-399.8\) & \(454.50\) & \(0.11\) & \(1.324\) \\ \hline CMC 10 & \(-1075.5\) & \(548.8\) & \(-162.5\) & \(666.76\) & \(87.79\) & \(1.011\) \\ \hline CMC 20 & \(-1061.5\) & \(185.4\) & \(-114.4\) & \(452.46\) & \(50.35\) & \(5.799\) \\ \hline CMC 30 & \(-1102.0\) & \(1027.3\) & \(-380.1\) & \(594.77\) & \(0.28\) & \(3.329\) \\ \hline CMC 40 & \(-1111.8\) & \(345.1\) & \(-174.8\) & \(604.40\) & \(87.50\) & \(1.007\) \\ \hline CMC 50 & \(-1135.2\) & \(318.8\) & \(-192.4\) & \(584.97\) & \(92.58\) & \(1.066\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Corrosion characteristics in linear voltammetry. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Element** & **Fe wt\%** & **C wt\%** & **O wt\%** & **Si wt\%** & **F wt\%** & **Mn wt\%** &
\begin{tabular}{c} **EDX** \\ **Error** \\ \end{tabular} \\ \hline Point 1 & 93.61 & 3.48 & - & 0.43 & 1.33 & 1.14 & 1.3 \\ \hline Point 2 & \multirow{2}{*}{74.07} & \multirow{2}{*}{2.78} & \multirow{2}{*}{21.70} & \multirow{2}{*}{-} & \multirow{2}{*}{-} & \multirow{2}{*}{1.45} & \multirow{2}{*}{0.5} \\ (Figure 9a) & & & & & & & \\ \hline Point 3 & \multirow{2}{*}{67.07} & \multirow{2}{*}{2.52} & \multirow{2}{*}{29.3} & \multirow{2}{*}{0.53} & \multirow{2}{*}{-} & \multirow{2}{*}{0.1} \\ (Figure 9a) & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Point analysis for areas with pitting corrosion. Figure 8: SEM analysis for the sample of improvement steel corroded in fresh CMC 2.5%: (**a**) \(200\times\) and (**b**) \(1000\times\). Improvement steel corroded in CMC 50: (**c**) \(200\times\) and (**d**) \(1000\times\). Figure 9: _Cont._  
Table 6 shows the chemical analysis of the first point on a surface not affected by corrosion, the second point on the areas with deposit conglomerates and the third point inside the pitting. There was a decrease in the percentage of Fe and an increase in oxygen, mainly due to the formation of oxides, but the presence of Cl and Si was a result of the formation of chlorides following the corrosion process. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Chemical Elements**} & **Fe** & **C** & **O** & **Cl** & **Mn** & **Si** \\  & **wt\%** & **wt\%** & **wt\%** & **wt\%** & **wt\%** & **wt\%** & **wt\%** \\ \hline Point 1 (Figure 10a) & 88.11 & 1.99 & 9.89 & - & - & - \\ \hline Point 2 (Figure 10a) & 77.09 & 1.27 & 18.82 & 2.05 & - & 0.75 \\ \hline Point 3 (Figure 10a) & 72.57 & 1.65 & 19.37 & 5.77 & 0.61 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Spot analysis for areas with pitting corrosion. Figure 10: _Cont._  
Figure 9: EDX analysis of corroded steel in CMC: (**a**) spectrum with chemical composition and element mapping (Fe, Mn, Cr, C, Si, O and F); (**b**) line analysis spectrum.