You will find consumable electrodes classified as bare, light, medium or heavily coated. The heavier the coating, the higher-quality weld the electrode will produce.
Consumable electrodes with different coatings result in different welding characteristics. Some coatings leave very little slag, while others deposit a protective coating on the welding seam. Still other types of coated consumable electrodes produce welds that cool quickly or work specifically with metals such as cast iron or stainless steel.
Consumable electrodes with specific coatings may require special handling, such as preheating. Other electrodes must remain dry and require baking before use to remove traces of water, which could interfere with the weld.