Nickel is a metal of secondary importance. Its principal use is in nickel alloys, notably nickel-steel, in plating, in coinage, and in the chemical reductions which call for apparatus made of a metal of inertness similar to platinum, but of greater cheapness.

The pure metal is harder than iron, melts at 1451 deg. Cent., slightly below iron, and is malleable and ductile. It resembles iron in being plastic at a bright red or white heat, and is readily weldable at that temperature. As the ordinary nickel of commerce is quite brittle, due to its impurities, it is seen that it will not weld. The welding property of pure nickel, however, is of importance in nickel plating and in making seamed nickel tubes.

One of the chief objections to nickel plate is its tendency to scale or peel off. Electroplated nickel-iron cannot be drawn, bent, or hammered with safety, and frequent changes of temperature will also tend to crack the nickel surface.

Theodore Fleitmann, of Iserlohn, Germany, took out a patent a number of years ago for making nickel-plated iron by mechanical means. Sheets of nickel and iron were heated to welding heat in an atmosphere of hydrogen, after having been polished and fluxed. They were then welded between rolls, without coming in contact with the air. By this method the natural tendency of both metals to oxidize quickly was prevented. At the welding heat the metals alloyed at the contact surfaces, and a plate was produced that could be rolled without detriment to the nickel surface.

In 1903, Thomas A. Edison took out a patent for a somewhat similar idea. The difference was that his nickel was electrolytically deposited, the plate was raised to redness in hydrogen gas by electric current, and then rolled. At first Edison plated iron sheets in a nickel solution, piled them together in a clay or cast-iron retort, and raised them to bright redness in a hydrogen atmosphere. At this temperature the metals alloyed and knitted at contact. They were cooled below oxidizing temperature in the same atmosphere before a new change of plates was admitted. Later, Edison improved his process by making it continuous. The iron, in a roll, was passed first through a chamber of hot hydrogen, which reduced all oxids and gave it a fresh surface. From this first chamber it passed into a cooling chamber of the same gas, then through the nickel bath, and the wash-tank; thence through a third hydrogen chamber, where it was raised to welding heat; and lastly to a cooling chamber of hydrogen. The speed was gauged to allow each step of the operation sufficient time.1

In 1905, the Standard Welding Company, of Cleveland, exhibited tubes of pure nickel welded electrically. The tubes were strong and the seam was invisible. The present demand for such tubes comes from automobile makers, rubber manufacturers for their end tubes, and industrial chemists for non-oxidizable tubes, retorts, and crucibles.