# Effect of Welding Parameter on the Corrosion Rate of Underwater Wet Welded SS400 Low Carbon Steel
## 3 Results and Discussion
Figure 10 shows the results of underwater welding EDS test with RB26 electrode. Point 5 shows O element content of 23.9%. Point 3 shows elemental O content of 7.6%. The P element found in the chemical composition of the electrode is used as a filler or additional metal which functions to increase the corrosion resistance of material so that the corrosion rate at the RB26 electrode is lower than the other two electrodes. This is also following the study of [PERSON] et al. [17]. The scholars said that the P element influences the corrosion resistance of the material so that the appearance of SEM is dominated by parts that have not been eroded (see Figure 10). Corrosion testing was also conducted to find the effect of the welding current used on the corrosion rate of the specimens. The compared welding currents are 100 and 110 A. The Tafel graph from the corrosion test for the ratio of current 100 A and current 110 A, is shown in Figure 11, while the comparison in forms of bar ratio of the corrosion rate is shown in Figure 12.  
Figure 11 indicated that welding with a current of 100 A has a Tafel curve higher than welding with a current of 110 A. The Tafel welding curve with a current of 100 A has an Ecorr value of \(-\)554.787 mV. In comparison, the Tafel welding curve with a current of 110 A has an Ecorr value of \(-\)582.122 mV. The welding Tafel curve with a positive value of \(E_{corr}\) results in a lower corrosion rate than the corrosion test specimens that have a more negative \(E_{corr}\) value. A higher Tafel curve results in a high \(E_{corr}\) value which tends to be more corrosion resistant. Figure 12 shows a lower corrosion rate found in welding with a variation of the welding current 100 A. The results of corrosion tests on underwater welding with an increase in welding current result in a higher corrosion rate. This phenomenon occurs because large welding currents affect the heat input value during the welding process. Current 100 A gives a corrosion rate that is smaller than 110 A because the higher the heat input value will cause a phase balance disturbance in the weld metal section. In contrast, a low heat input value may not achieve the desired weld penetration [23]. The input value of heat that is not excessive will push the polarization curve to a positive value so that it can provide better corrosion resistance [24]. Figures 5 and 12 show corrosion test specimens taken first in macros then enlarged with a magnification of 1500 times at their midpoint. The macro photo on welding with 100-A current shows darker color is more dominant than welding macro photo with  
Figure 11: Tafel diagram of underwater welded joints with parameters of different welding currents. Figure 12: Corrosion rate of underwater welded joints with parameters of different welding currents. 110-A current. This phenomenon proves that welding with 100-A current is more effective because it has a lower corrosion rate than welding with 110 A. The results of this SEM test are following the results of corrosion tests where the current 110 A has a higher corrosion rate compared to welding with a current of 100 A. The selection of the right heat input can reduce the amount of porosity in the weld metal. The more porosity will cause stress concentration to occur, which is the beginning of the formation of pitting corrosion [16]. The elements contained in the specimens resulting from corrosion tests can be seen in Figure 10. The darker colored parts contain less oxygen because the protective layer has not been damaged so that the corrosion process has not occurred. The brightly colored part contains more oxygen because the protective layer was damaged so that the corrosion process occurs. Water depth parameters also influence the corrosion test results. Therefore, corrosion testing was also carried out at a depth of 5 m and 10 m with a fixed electrode E7016.