Arc welding electrodes are coded by the American Welding Society (AWS). Each AWS number gives specific information about the electrode.
Classification of mild and low alloy steel electrodes are based on an "E" prefix and a four or five digit number. The first two numbers (or three if it is a five digit number) indicate the tensile strength in thousands of pounds per square inch (psi). The next digit indicates the welding position in which the electrode is capable of making a satisfactory weld (1= All position; 2= Flat or horizontal). The last digit indicates the type of current to be used (AC, DC-, OR DC+) and the type of coating on the electrode (Organic, Rutile, Low Hydrogen, Mineral Iron Powder, or Low Hydrogen Iron Powder).
For Example: E7018
E - indicates arc welding electrode
70 - indicates a minimum of 70,000 psi tensile strength
1 - indicates the electrode can be used in all positions
8 - indicates the electrode is coated with a low hydrogen, iron powder and can be ran either in AC or DC+ current.