Electrodes make an essential element in arc welding. Each of the methods used for arc welding will use a unique electrode to generate the necessary fusion of your materials. Coated electrodes are primarily used for SMAW (shielded metal arc welding) or stick welding. The coating on these electrodes is approximately 1-3mm thick and comprises 15-30% of your electrode’s weight. Electrode coatings are meant to improve your welding arc’s stability, generate a protective gaseous environment for molten metal, and provide flux that helps in the removal of oxides and other impurities.
The coatings used on the products from welding wholesale suppliers also minimize welding spatter and slow down your weld’s cooling rate. Electrode coatings comprise metal, organic materials, minerals and binders. The minerals protect your electrode from atmospheric elements, while organic products produce hydrogen that is beneficial for your weld’s positive characteristics. Binders enable a solid coating for your electrodes while metal will strengthen your coating.
The following are the classifications used for welding electrode coatings:
These are considered the gold standard in coated welding electrodes. This is because they have optimal arc stability, will transfer metal in fine drops that have low spatter levels and low fume emissions, and have a smooth restart from cold. Rutile coatings are often used for low carbon steels to generate strong welds with the best mechanical properties. Some manufacturers add cellulose to their rutile coatings to create an extra gas shield for a strong weld.
Low Hydrogen Coatings
These contain fluorites and calcium carbonates. The coated electrode in this instance should meet the required steel properties for its intended weld, including the CTOD, creep and impact and tensile strength, among others. Moreover, the achieved chemical balance of your electrodes should be robust. This means it should meet a range of thermal cycles and withstand the variations in different welding procedures.
Lastly, a basic electrode coating should have a diffusible hydrogen content that is as low as possible to avert the cold cracking of your weld. This coating is ideal for low carbon, low alloy, and high strength steels.
These comprise organic materials, though cellulose is the primary element in them. Cellulosic coatings have the same properties as rutile coatings, but there is a lower titanium oxide content in the former. Cellulose coatings also have a deeper penetration rate than rutile coatings. As cellulose burns, it generates carbon monoxide and hydrogen. These create a protective shield to your base metal.
Iron Oxide Coatings
These have improved bead appearance and arc behavior. Iron oxide coatings also have a positive impact on your metal’s deposition rate and the speed of your arc’s travel. Their hydrogen gas evolution is also less compared to that of cellulosic coatings, though its penetration rate is lower than the latter. Iron oxide coatings are generally used for positional welding.
Some welders assume that any coated electrode will suffice for their tasks. This leads them to settle for the cheapest or most readily available electrodes on the market. Anything less than the best supplier for your welding electrodes regardless of their coating from the above, however, leaves you with low-quality welds.