Wednesday, May 16, 2012

Process Wednesday: what the heck is Hastelloy?

It took me a while to figure out the different types of reactor metals that a typical plant has. There's the classic Pfaudler glass-lined steel (with its lovely purple hue), there's stainless-steel reactors and then there's Hastelloy. What the heck is Hastelloy, anyway?

According to Wikipedia (and Haynes International, the manufacturer of Hastelloy), it's basically corrosion-resistant nickel that's alloyed with other metals:
The predominant alloying ingredient is typically the transition metal nickel. Other alloying ingredients are added to nickel in each of the subcategories of this trademark designation and include varying percentages of the elements molybdenum, chromium, cobalt, iron, copper, manganese, titanium, zirconium, aluminum, carbon, and tungsten. 
The primary function of the Hastelloy super alloys is that of effective survival under high-temperature, high-stress service in a moderately to severely corrosive, and/or erosion-prone environment where more common and less expensive iron-based alloys would fail, including the pressure vessels of some nuclear reactors, chemical reactors, distillation equipment, and pipes and valves in chemical industry. (Emphasis CJs) Although a super alloy, Hastelloy does experience degradation due to fabricating and handling. Electropolishing or passivation of Hastelloy can improve corrosion resistance.
Good to know.

8 comments:

  1. It's not as corrosion resistant as one might think. Before carrying out any prolonged batch campaign we had to do corrosion testing if we were using any alkyl halides, or acids and the like.
    We had a special tantalum reactor for azide chemistry.

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  2. Both tantalum and Hastelloy are nice, nearly universal reactor materials. In heat transfer the all-metal reactors beat the glass-lined alternatives hands down.

    I am happy to see this post. In a fast paced, lean environment it may be hard to pay attention to the materials in contact with the process. Finding a chunk of spalled PP or high metal content in a scaled-up finished product is no fun.

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  3. As always, thanks to the both of you for sharing your expertise.

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  4. HCl, HBr gas and aqueos HCl solutions above 0.5 M are quite mean to stainless steel and Ni-based "corrosion resistant" alloys like Monel. Not only this can damage expensive equipment but it can also cause unacceptable Ni(2+) carryover into the product. I had one particularly memorable incident with manufacture-defect Monel alloy regulator for HCl tank that sprung a gale-force leak into the lab (the anh HCl gas tank was too big to fit in the hood. The HCl cloud filled the lab with a corrosive fog in one whoosh). The Monel parts were impressively corroded and pitted from this incident

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    Replies
    1. As a "second" to the above, let me be the first to admit that the best way to learn to not put halogen salts in a stainless steel reactor is to ruin a brand new stainless steel reactor by putting halogen salts in it.

      I speak from first-hand experience. Hastelloy ftw!

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  5. Just keep in mind that there are many different grades of hastelloy available. One might be perfectly suitable for your reaction conditions while the other grade turns your reaction mixture into a greenish nightmare. Haynes and other steel manufacturers have material compatibility lists available that can give you a general idea on the stability. Concerning acid resistance, nothing beats reactors lined with solid graphite bricks (not really your favourite reactor to isolate APIs), heat transfer is an absolute nightmare though.

    One of the many pitfalls in a plant environment is that your reactor might be perfectly compatible with your reaction conditions, but really look for material compatibility of your peripheral devices (transfer pipes, pumps, heat exchangers etc.)

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