Consumable electrodes melt and drip down onto a work piece. The drops form a pool that creates an effective weld when cooled. In TIG welding, the electrodes stream a live electric current down to a work piece, but do not melt onto the work piece.
The 6010, 6013 and 7018 electrodes are some of the most versatile and widely-used electrodes. General welding applications can be executed with 6010 electrodes. These electrodes are also used on piping, wrought iron, farm and road equipment. The 6013 electrode creates a soft arc at the tip of the electrode. This electrode is designed for working with sheet metal or for repairing thinner materials. For crack-resistant, high-quality welding, 7018 electrodes are commonly used.
The AWS (American Welding Society) has created a universal identification system for electrodes in the U.S. This system allows the consumer to easily identify the proper electrode for applications. An electrode's first digits indicate tensile strength. For example, 6010 electrodes produce welds that offer 60,000 psi (pounds per square inch) tensile strength. The second-to-last digit in an electrode identification number indicates the position in which the operator must hold the electrode while welding. For example, a "2" would tell the welder that the electrode must be held in a horizontal position. The final identification number indicates the type of outer coating on the electrode.
Coating an electrode with certain materials increases welding efficiency. For flat welding applications, the welder may choose an electrode with an iron oxide coating that promotes a stable electric arc. Electrodes with a rutile coating promote a smooth, quiet electric arc. The AWS identification system indicates an electrode's outer coating. Electrodes with a "1" as their last identification number are coated with a cellulose potassium coating; electrodes with a "5" feature a low hydrogen sodium coating. Low hydrogen electrodes, like the 7018 electrode, feature low-moisture coatings to curb the amount of hydrogen in a weld.