Around this time, an American named C.L. Coffin secured a patent for metal electrode welding, and N.G. Slavianoff of Russia used the same method for casting metals. In 1900, stick welding became more popular through the use of a coating of lime on the welding stick to make the arc much more stable. CJ Holstag invented the alternating current in 1919, but it wasn’t commercially used by the welding industry until the 1930’s. In 1920 though, P.O. Nobel introduced automatic welding, which integrated the use of arc voltage and bare electrode wires, and there were also several types of electrodes developed during this decade. In 1930, stud welding, smothered arc welding, and submerged arc welding were introduced. The New York Navy Yard was the one who developed stud welding, while the National Tube Company developed smothered arc welding. Although the New York Navy Yard developed stud welding, it was later replaced by the more advanced submerged arc welding in the sector of shipbuilding, while it was still widely used in the construction industry. Another historic milestone was hit in 1941 when a new process was created by Meredith. This process was used for seamlessly welding aluminum and magnesium, and was called gas shielded metal arc