Flux coatings serve several functions. They determine how the electrode will act during periods of operation. Some coatings are designed to burn, smoke and act as a shield to protect the air around the pool of liquid metal that forms and cools at welding points. Parts of an electrode's flux melt onto a work piece along with the electrode during welding. The flux floats impurities to the surface of a weld pool. These impurities can easily be removed after the weld pool cools. Flux in general contributes to a strong and durable weld.
The American Welding Society offers a classification system that helps consumers identify electrodes and their proper applications. Two common types are 6011 and 7014 electrodes. As outlined by the AWS, the first two or three digits in an electrode's identification number indicate the tensile strength of the welds they can create in thousands of pounds per square inch. 6011 electrodes for example, produce welds that offer 60,000 psi tensile strengths. The third digit indicates the position that the welder should hold the electrode in while welding --- horizontal, vertical or any position. The final two digits in an electrode's identification number indicate the type of flux coating applied to the electrode.
Electrodes that end in "10" feature high cellulose sodium coatings. 6010 electrodes are ideal for use on piping and wrought iron. Electrodes ending in "11" feature high cellulose potassium coatings. Type 6011 electrodes are ideal for work on bridges, farm equipment; they feature high cellulose potassium coatings. High titania sodium coatings and high titania potassium coatings are indicated by the digits "12" and "13," respectively. Iron powder titania coated electrodes end in "14" while low hydrogen sodium coated electrodes end in "15."
Type 7014 electrodes feature iron powder titania coatings. Electrodes ending in "16" feature low hydrogen potassium coatings, electrodes ending in "27" feature an iron powder iron oxide coating and electrodes that end in "18" feature an iron powder low hydrogen coating. The number "20" indicates a high iron oxide coating and "24" indicates iron powder titania coatings.
Electrodes that feature a more heavy coating of flux produce deeper penetration and higher quality welds. Heat can be more focused while using heavily coated electrodes because live electricity is more constricted under a heavy coating of flux. Cellulose-coated electrodes offer an increased burn-off rate and impart deep penetration. Electrodes with iron oxide coatings offer great weld appearance. Electrodes with titania coatings produce little spatter and promote a smooth, quiet electric flow between electrode and work piece. Iron powder coatings also promote smooth, steady electric flow between electrode and work piece. Low hydrogen coatings promote welds that are resistant to cracking.