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Comment Processing & Handling

Specialty Metals

By Department Editor: Kate Torzewski |

One of the most important factors to consider when evaluating a specialty metal for use in valves, fittings and instrumentation is its corrosion resistance or corrosion rate of the metal in the target media. Each material discussed here has its own niche, and depending on the processing environment and the needs of the application, the metal’s strengths and weaknesses may or may not be suitable. In either H2SO4 or HCl solutions, the corrosion resistance of tantalum is second to none, followed by zirconium, nickel alloys and titanium. Thermal expansion coefficient and melting point data for each metal are given in the table. Tantalum The physical properties of tantalum are similar to those of mild steel, although tantalum has a higher melting point. Tantalum is the most corrosion-resistant metal that is in common use, due to its tenacious oxide layer. Its superb corrosion resistance is comparable to glass and is practically inert to most oxidizing and reducing acids, except fuming sulfuric acid, hot alkalis and HF. While tantalum is an ideal choice from a corrosion-resistance point of view, it is typically cost prohibitive, even when cladded. Only in process conditions where no other material will perform adequately is tantalum…
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