MMA - Manual Metal Arc (Welding)
MMA is a mode of arc welding with consumable electrode. At welding with coated consumable electrode the welding joint is formed due to melting by arc the electrode and edges of basic metal. As an electrode the metallic rod from the same or similar to welded metal is used. There is the electrode covering coated on the metallic rod; in the melting this covering forms slag which protects the metal of joint against oxygen and nitrogen of atmosphere air and eliminates bad admixtures from melted metal.