# Effect of Welding Parameter on the Corrosion Rate of Underwater Wet Welded SS400 Low Carbon Steel
## 3 Results and Discussion
The formation of coarse columnar granules causes mechanical characteristics to decrease so that the corrosion rate of underwater welding will be higher than the speed of ground welding. The results of corrosion tests on underwater welding with a comparison of welding electrodes used showed a corrosion rate on the RB26 electrode lower than the corrosion rate on electrodes E7016 and RD26. The element phosphorus (P) in the electrode affects the corrosion resistance of the material. Table 1 shows RB26 electrodes having a P element composition of 0.012%, 0.001% more than other electrodes so that it has a slightly better corrosion resistance than other electrodes. This phenomenon is matched with the research of [PERSON] et al. [17], who stated that the P element is influencing a better corrosion resistance of the material. The sulfur element (S) found in the electrode also influences the characteristics of good weld penetration even though it adversely affects heat treatment, cold resistance and corrosion resistance pitting [18]. Table 1 shows that RD26 electrodes have a high elemental composition of sulfur compared to the other two electrodes which is as much as 0.02%, thus influencing the high corrosion rate that \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Electrode**} & \multicolumn{5}{c}{**Chemical Composition**} \\  & \multicolumn{3}{c}{**(in Percentage by Weight - wt\%)**} \\ \cline{2-6}  & **C** & **Si** & **Mn** & **P** & **S** \\ \hline E7016 & 0.07 & 0.55 & 1.05 & 0.011 & 0.006 \\ \hline RB 26 & 0.08 & 0.30 & 0.37 & 0.012 & 0.010 \\ \hline RD 26 & 0.08 & 0.3 & 0.5 & 0.02 & 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Electrode composition (KOBELCO welding consumables and NIKKOSTEEL quality & technology). Figure 3: Corrosion rate of weld joint with electrode parameters and 100-A electric current. occurs in the weld using the electrode. Much porosity happens in underwater welding results and is one of the essential causes of pitting corrosion. Pitting occurs when the electrolyte starts transporting ions between the anode and cathode. If only a small amount of metal is eroded, this is usually referred to as localized corrosion [19]. The specimens resulting from corrosion testing were then tested by SEM and EDS to see the surface topography and the distribution of chemical composition of intermetallic matrix and particles. Figures 4-7 show corrosion test specimens taken first macros then magnified 1500 times at the midpoint. The macro photo on welding with RB26 electrode shows many dark colors which means that the area has not been corroded entirely because the protective layer is still firmly attached to its surface, it was different from welding using E7016 and RD26 electrodes which shows many bright colors, which is a sign of a protective layer already damaged by chloride ions so that corrosion is rapid and occurs locally. Figures 4-7 also show the SEM display of test specimens corroded with variations in welding electrodes, while Figures 8 and 9 present macro photo of the tested welds. Figure 7: SEM display in welding with RD26, 2.5-m depth and 100-A current. Figure 8: Macro photo of the tested welds: Part 1–100-A current. Underwater welding has several adverse effects, namely, the high cooling rate and a large amount of diffused hydrogen [20]. [PERSON] et al. [21] said the cooling rate in underwater welding is higher than ground welding. Hydrogen trapped inside the weld metal will cause porosity [22]. One of the defects that occur in underwater welding is porosity defects which are also one of the causes of pitting corrosion [12]. Welding defects that arise in underwater welding can worsen the corrosion resistance of a material. This defect usually causes an initial pitting and crevice attack on weld metal [16]. Underwater welding has a higher risk of cracking than ground welding. High cooling rates cause surface damage due to corrosion which is characterized by cracks. Figure 9: Macro photo of the tested welds: Part 2–110-A current.