# Effect of Welding Parameter on the Corrosion Rate of Underwater Wet Welded SS400 Low Carbon Steel
## 3 Results and Discussion
Figure 13 shows a Tafel graph of the comparison of depth parameters and Figure 14 shows a bar diagram of the ratio of corrosion rates to water depths of 0 m, 2.5 m, 5 m and 10 m with a welding current of 100 A. The lowest corrosion rate is obtained by welding with a variation of 2.5-m depth which is equal to 0.10536 mm/year. The highest corrosion rate is obtained by welding with a depth variation of 10 m which is equivalent to 0.12538 mm/year. The results show that the corrosion rate in underwater welding increases with increasing welding depth. The reaction between electrodes and water (H\({}_{2}\)O) in underwater welding results the appearance of porosity in the welding specimens. Figure 13: Tafel diagram of underwater welded joints with E7016 electrodes and 100-A currents. The metal-microstructure phase is dominated by ferrite and pearlite. Increasing water depth causes microstructure that looks more refined because the cooling rate increases and the size of the grain shrinks. Underwater welded joints have more defects compared to welded joints on land. Poor arc stability and the result of the dissociation of water in the form of gas trapped in the weld metal is the leading cause of many defects in underwater welded joints (see Figure 15). The increasing depth of water results in the cooling rate also increasing and can adversely affect the results of underwater welded joints [25]. [PERSON] et al. [26] and [PERSON] et al. [27] stated that porosity in  
Figure 3:0 Corrosion rate in underwater welded joints with E7016 electrodes and 100-A electric current. Figure 3:1 Weld metal states for different welding conditions. (**a**) land-based welding; (**b**) underwater welding using electrode E7016; (**c**) underwater welding using electrode RB26 and (**d**) underwater welding using electrode RD26. underwater welding occurs because of an increase in the amount of oxygen and hydrogen. Negatively charged chloride ions play an essential role in the oxidation process on metal surfaces. Anodic and cathodic reactions that occur in successive pits, namely:  
Figure 3:2  
Figure 3:3  
Chlorine compounds in the electrolyte solution will react with \(\mathrm{Fe}^{3+}\) ions and form a solid oxide layer (\(\mathrm{Fe}_{2}\mathrm{O}_{3}\)) which covers the anode surface so that corrosion occurs. As a result of the above reaction, the pit or hole becomes positively charged so that it contrasts with the electrolytes around the negatively charged pit. This positively charged pit will attract Cl- negative ions so that it can increase the acidity of the electrolyte so that it speeds up the corrosion rate [28], this is following the reaction:  
Figure 3:4  
Water depth in underwater welding affects the corrosion rate of welding results. The deeper the welding is done; the water pressure will also be more significant and will make the welding arc unstable so that it affects the results of welding. Moreover, the amount of oxygen and hydrogen in the welding pool is increasing due to water dissociation, which results in porosity and hydrogen cracks [26; 27]. Water dissociation that occurs during the underwater welding process is an abundant source of hydrogen gas in the area around the welding arc, which quickly spreads to the weld pool. Water pressure under underwater welding conditions significantly affects the physiochemical balance in the weld pool. High levels of cooling cause susceptibility to phase transformation at HAZ, the presence of slag and the appearance of porosity. The high content of hydrogen in the metal will cause the formation of hydrogen crack, which is one of the causes of corrosion [21]. Influences of the selected parameters in this study are also quantified in terms of chemical composition, especially Fe, which is a fundamental element of metal. As presented in Figure 16 for applied currents, which it can be observed that higher current caused a difference in Fe composition, which 110 A produced lesser Fe wt% compared to 100 A with gap approximately 7.42%.