# Effect of Welding Parameter on the Corrosion Rate of Underwater Wet Welded SS400 Low Carbon Steel
## 1 Introduction  
Welding is a metal joining process which has a crucial role in the manufacturing industry. This process applies heat on the joined metals, so they are melted, fused and joined. This process usually requires a filler metal and sometimes requires pressure to help the joining process of metals [1; 2]. Under certain conditions, underwater welding is needed, even recently, underwater welding is widely used for maintenance and repairing the damage of underwater structures and underwater pipelines to extend the lifetime of these facilities [3]. For example, underwater welding has been applied to the maintaining of nuclear power equipment. Water is a moderator and cooler in a nuclear reactor. For maintaining the nuclear reactor, the underwater welding process must be conducted to prevent pollution of nuclear radiation [4]. Another application of underwater welding is for retaining the offshore platform structures. Managing of these structures usually requires special underwater repair operations. Although several other methods can be used, underwater welding is still considered one of the best practices based on economic reasons. Based on the principle of the welding process, two types of underwater welding, underwater dry and wet welding processes are well known. Underwater dry welding is a method of underwater metals joining in a weld chamber which is conditioned in a sterile environment. Weld chamber is usedto avoid the adverse effects of water and ensure that welding quality is similar to welding joint on land. Underwater wet welding is an underwater welding process which uses a particular waterproof stick electrode. It is carried out directly underwater, so the arc is surrounded by the water environment. Underwater wet welding generally is recommended due to its advantages including equipment is simple, the welder can more easily mobilize welding equipment in water, the preparation process required is fast, the operation is smooth, and the operation costs is cheap. However, the underwater wet welding (UWW) technique also has disadvantages including a decrease in material ductility, increase material hardness in the heat-affected zone (HAZ) area, defects in the weld metal, weld arc instability and the presence of water waves around the welding area. These can be a significant problem because they affect the underwater welding joint, which is susceptibility to crack propagation, high porosity and low mechanical properties. There are many kinds of welding technique for underwater welding application including manual metal arc, flux cored arc welding, gas metal arc welding, etc. The most popular technology for underwater welding application is manual metal arc (MMA) welding due to it is simple and low cost in equipment and operational. However, it will cause problems where metallurgical quality and weld defects are often found and very dependent both on the welder skills and weld parameters [5]. It is essential to evaluate the properties of underwater MMA welding based on its settings, including weld current and electrode type. Weld current will affect the arc stability, penetration, heat input and HAZ width [6; 7]. The electrodes of MMA welding can be classified based on the electrode coating in which it will obtain varies in mechanical properties and low hydrogen diffusible levels of weld metal [8]. Due to the hygroscopic property of the electrode coating, the electrode is still requiring special treatment before being used to avoid the hydrogen diffusion into weld metal. Underwater structures are placed in an underwater environment and subjected the corrosive fluid such as seawater with a certain level of salinity. Base metals, HAZs and weld metals of underwater weld joints have different potential to lead the corrosion process to occur. It means that underwater welding process will affect the corrosion resistance of joint area significantly because it is related to the heating and cooling rate as well as the coating type of electrode in underwater welding [9; 10].