• Whenever two materials are being permanently fused together through the process of either MIG or TIG welding, there is typically a choice in the welding machine between using an AC or DC current. In many cases, the choice most welders prefer is AC current because of the amount of penetration this type of current provides. Running the current from the welder through the welder's tip helps the electrode to bond with the material. The current is then sent back into the welding machine, doing the exact opposite action. This repetitive exposure to the current achieves deeper, more consistent welds. This is an especially favorable type of current for welding aluminum or alloyed materials because of its natural tendency to rid the welding material of any impurities it may contain. That doesn't mean that anyone can pick up an AC welding torch and start welding; you need to be prepared and know what you're doing during the process.
  
  

Selecting the Amount of Current for the Weld

• In order to provide sufficient voltage to the welding electrode to produce enough heat to weld properly, the right amount of voltage must be set through the controls on the welding machine before the electrode is applied to the material. If this step is not conducted properly, the weld may fail due to insufficient fusion from the lack of proper heating. It can also result in the weld not attaching the materials at all, while still allowing the welding stick to melt and apply to the work piece. Because of this, it is imperative that the person performing the work knows exactly what each setting on the welding machine means and how to apply it to different materials and welds.
  
  

Knowing the Material

• Another factor that must be taken into consideration when performing any kind of weld, but especially when working with AC welders, is the type and condition of the material being welded. Steel and aluminum, for instance, have different properties and as such they must be both prepared and welded differently. In most cases, a larger electrode must be used in order to effectively weld aluminum, mainly because of the metal's natural property in being a better electrical conductor than steel. This usually means that while more heat is required to weld steel, more voltage or power is required to weld aluminum.
  
  

Shaping the Welding Tip

• One of the easiest ways to produce a consistent and strong weld is to make sure that the applied end of the tungsten welding rod forms a ball at its end before applying it to the seam to be welded. This shape will allow for the ball to evenly coat the seam, also allowing for the best amount of penetration into the seam, which is important in matters of weld integrity.