Metallurgy brazing

Other areas of corrosion concern are the membrane seals. If the seals are composed of flexible graphite, a preferred sealing material as discussed above, then corrosion by the common feed stream constituents is not a problem. However, with any metal seal - whether it be a brazed, welded, or soft-metal gasket seal - it is prudent to evaluate the potential for corrosion specifically at the seal. This evaluation is complicated by the fact that with brazed and welded seals, the metallurgy of the seal is influenced by the addition of the membrane alloy to the liquid braze alloy or weld pool. Experience has shown that welded seals to Pd—40Cu membranes, in which the membrane is welded to either Monel or 304L stainless steel, rapidly fail when subjected to 50 ppm hydrogen sulfide at 400 °C. 

Industrial applications. Typical uses are as protection sheath for immersion thermocouples used in nonferrous metal melting, immersion heater and burner tubes, degassing and injector tubes in nonferrous metallurgy, metal feed tubes in aluminum die casting, welding, and brazing fixtures and pins. 

Lancaster, J. F., Metallurgy of Welding. Brazing and Soldering, George Allen and Unwin, London (1970)... 

Boric acid is used to make heat-resistant glass. It is used in porcelain enamels and glass fibers. Boric acid is also used in metallurgy, in welding flux, and in copper brazing, in addition, boric acid is used in flame-retarding textile products. 

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