Cut the Hassle: Hastelloy C-22 vs. C-276

Material selection can be a difficult decision when you don’t understand the differences between two materials with almost the same cost.

Have you ever asked for Hastelloy C-276 material and been recommended Hastelloy C-22 instead?  Have you wondered what the difference is between them, and why one should be preferred over the other?

Here are few reasons why C-22 is a better choice than C-276:

Hastelloy C-22 has a better overall corrosion resistance compared to Hastelloy C-276.

The life of the material—and eventually the costs—depends on its ability to withstand different environments. Looking at the chemical composition of these two materials, C-22 is about 22% chromium and C-276 is 16% chromium. This 6% difference provides C-22 with a better corrosion resistance than C-276 in oxidizing environments, improving the life of the material by 5-10 times.

Now, where would you find the oxidizing environments? Some of the severe oxidizing mediums are sodium chloride (NaCl), hydrochloric acid (HCl), and sulphuric acid (H2SO4). C-22 also shows outstanding resistance to ferric and cupric chlorides, acetic anhydride, formic and acetic acids, hot contaminated organic and inorganic acids, brine solutions, seawater, etc.

C-22 has been found to have outstanding resistance to pitting, crevice and stress corrosion cracking when compared to C-276.

Both C-22 and C-276 have been tested in the oxidizing mediums for pitting and crevice corrosion. It has been proven that C-22 is more resistant to the oxidizing media, even at higher temperatures, than C-276.  However, in the reducing environments both C-22 and C-276 behave the same. A few of the reducing agents are oxalic acids (C2H2O4), formic acids (HCOOH), phosphorous acid (H2PO4), etc.

C-22 weld filler materials provide better weldability and over alloying ability, thus improving the corrosion resistance.

Many customers complain about the corrosion in their welds, but C-22 weld filler materials have been very successful in addressing these concerns.  Not only is C-22 resistant to oxidizing and reducing environments, but also to the inter-granular corrosion in the heat-affected zone (HAZ) of weldments.

Upon exposure to oxidizing sulphuric acid solution, C-22 faced very nominal corrosion attack.  Conversely, C-276 suffered severe base metal, weld metal, and HAZ attack.

When tested in the saturated wet chlorine environment as a function of temperature, C-276 corroded very severely in the weldments during the vapor phase as well as the liquid phase.  C-22 withstood higher temperatures in the same phases.

Each of these factors support the fact that Hastelloy C-22 should be the choice for longer life and better performance when selecting the material for your process.

15 comments

  1. mb says:

    NaCl and HCl are not oxidzing environments! HCl is a reducing acid and only con sulfuric acid is an oxidizing environment!

  2. Spencer says:

    Are you sure? In the Lewis definition of acids isn’t the fact that acid gets reduced what makes it an acid?

  3. Yes, according to the Lewis definition there is a possibility of competing reaction pathways depending upon which reactants are present and the relative energies of the possible products. As a result a compound may serve as an acid, base or an oxidizing agent or a reducing agent depending on the reaction.

    What we want to emphasize here is that Hastelloy C-22 can withstand both the oxidizing or reducing environments or oxidizing or reducing mediums/agents.

  4. sanjay says:

    If HCl gas is used which material would you recommend Hestalloy C – 22 or C-276?

  5. Technically, Hastelloy C-22 performs a little better in some environments compared to Hastelloy C-276. When it comes to recommendations, it depends on many factors. Your specific conditions will determine what material is suitable for your applications, and material testing labs could be a great source for helping you make this decision.

    The purpose of this article was to compare the differences between Hastelloy C-22 and Hastelloy C-276. I also wanted to illustrate that C-22 is a slightly upgraded version of C-276, according to several laboratory tests performed in liquid chloride environments. This article is not meant to be a deciding factor for your individual application.

    If you have more questions, you can submit them here http://csidesigns.com/flowgeeks/contact-us-2/ and I will be happy to continue our conversation.

  6. I am looking for a PHE for cooling diluted Sulfuric Acid, 1.84 g/cc to 1.26 g.cc. We cant afford any metalic contamination. We are also considering using a PE Heat Exchanger but rate of heat transfer will be very low, so I am considering a Hastelloy C276 is one choice. What’s your recommendation? Thanks.
    Mukesh

  7. Prasad K Krishnan says:

    Namaste Yogini gi

    As a research scholar, can you suggest me the cutting parameters like feed ,speed, depth of cut , tool material and tool holder specifications for turning experiment on C-c22 hastelloy.

    Prasad K K

  8. Vipul Modi says:

    What is the difference in terms of Price for 1 meter pipe length of Hastelloy C-276 and C-22? Is it a majot factor to decide while selecting the material?

  9. sandal says:

    shall we used the hastalloy c 276 in high temperature max 200 c in h2so4 acid

  10. Vinay Desai says:

    How much C-276 is susceptible to Stress corrosion Cracking in reducing environment at higher pressure of 47 bar & temperature of 200 DegC , having presence of halogen like Methyliodde & Hydrogen iodide.
    Which is better Material than C-276.

  11. Muskaan says:

    True that. Completely agree with you. Even in wet chlorine environments hastelloy C-22 alloy is significantly more resistant to than hastelloy C-276.

  12. Yogini Dhopade says:

    Sandal: Temperature is just one aspect, you need to consider the concentration and some other external factors as well. It is a combination of properties. You may be better off getting it tested. What is your application?

    Vinay: For your specific requirement, I would suggest you to get tested. Stress corrosion cracking is one such phenomena where the environmental factors plays major role. It does with other corrosion mechanisms as well but with Stress corrosion cracking it is a combination of the stresses produced and the product environment of temperature, concentration of the chemicals etc. The detailed corrosion mechanism will differ based on these process, just not the pressure, it could be any mechanical properties such as tensile stresses, operating stresses, the area where there could be maximum stress etc..combined with the corrosive environment that could lead to stress corrosion. Have you seen stress corrosion cracking with this material before or with other material? Have you tried to look if there are other factors involved? Have you considered it getting tested for the exact environment?

  13. Yogini,
    Nice article.

    We have a failure case where Hastelloy C276 has been badly corroded. Service is 35%HCl.

    It is 35% HCl being used in cold condensate polisher unit of Boiler. HCl is being used to maintain pH of the condensate. Severely corroded item is a PRV (pressure relieving valve) installed on HCl pump discharge line. Material of PRV is Hastelloy C276, wrought form. Valve internal are so badly corroded that, if you touch it, it is powdery deposit you can feel on your fingers.

    Temperature of HCl is ambient whereas, during peak summer season in Middle East (Qatar), it may reach to 50 Deg C.

    Lab analysis of our acid tank is as below: Conc.= 32.7%; Fe = 8.2 mg/l and Cu = 0.27 mg/l.

    Have you experience such failure before? What is alternative for my stream of 35% HCl? Since it is a PRV (pressure relieving valve), I am not sure, if I can go to non-metallic?

    Appreciate your thoughts and facts on this case.

    Regards
    Sandeep, corrosion engineer, Qatargas.

  14. Mam, Thank You for the post. It has proven to be very helpful as sometimes it is difficult to choose the correct alloy. The points stated are also true and I totally agree with them.

  15. SS 904L Pipe says:

    Completely agree with all your points. It was pleasure reading your post. Nicely written and presented.

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