In certain industrial applications, such as the production of fiberglass wool for preparing thermal or acoustical insulation products, there is a need for metal alloys which posses certain characteristics such as high rupture strength, high corrosion resistance, and high oxidation resistance at elevated temperatures. In the fiberglass and mineral fibers industries, filaments which may be used for preparing such insulation products are produced by passing molten glass or mineral through the bores of the foraminous wall of a chamber which is adapted for rotation at high angular velocities (said chamber being known as a fiberglass spinner). The filaments are extruded through the fiberizing bores due to the centrifugal action of the rotating spinner. Such spinners are typically operated at a temperature of about 2,050.degree. F. and an angular velocity of about 2,050 RPM. It is advantageous, from a fiberglass production cost standpoint, for the angular velocity to be as high as possible so as to maximize the rate at which filaments are extruded through the fiberizing bores. However, high spinner angular velocities result in reduced spinner life due to the limited corrosion resistance of typical spinner base metal alloys. The flow of molten glass or mineral through the spinner bores corrodes the cylindrical walls of the bores causing them to enlarge, resulting in a loss of control of fiber diameter.
It is well-known in the fiberglass manufacturing art to apply a layer of platinum or other precious metal or alloy over the surfaces of base metal components which contact the molten glass, to reduce the corrosion of the base metal alloy by the glass. The bores of fiberglass spinners are especially susceptible to corrosion caused by molten glass. Johnson, D. C. "Platinum Coating Technique Developed for the Glass Industry," Glass, September 1987, page 372 discloses a method for applying a platinum coating to the surfaces of fiberglass spinner bores. The platinum coating is bonded directly to the spinner base metal alloy. Platinum and other precious metals are expensive, however, and therefore dramatically increase the costs associated with producing a corrosion-resistant spinner. Moreover, it has been found that platinum coatings result in an undesirable interdiffusion zone of complex intermetallic compounds which forms near the interface between the precious metal layer and base metal alloy.
It is known that an alloy comprising chromium and nickel, wherein the chromium concentration is above about 30 weight percent, is highly resistant to corrosion by molten glass. However, such chromium/nickel alloys, having high concentrations of chromium, as coatings for the surfaces of fiberglass spinner bores are unknown. U.S. Pat. No. 4,028,116 to Cedarleaf discloses a method for codepositioning chromium and nickel by electroless plating, wherein the achievable concentration of chromium is only up to 30% by weight.
It must be noted that the prior art referred to hereinabove has been collected and examined only in light of the present invention as a guide. It is not to be inferred that such diverse art would otherwise be assembled absent the motivation provided by the present invention, nor that the cited prior art when considered in combination suggests the present invention absent the teachings herein.
It would be desirable to coat the bores of a base metal alloy fiberglass spinner with a non-precious metal corrosion-resistant material.