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Corrosion-Resistant Alloy (CRA)

Last updated: April 6, 2020

What Does Corrosion-Resistant Alloy (CRA) Mean?

A corrosion-resistant alloy (CRA) is an alloy consisting of metals such as:

  • Chrome
  • Stainless steel
  • Cobalt
  • Nickel
  • Iron
  • Titanium
  • Molybdenum

When combined, such metals can promote corrosion resistance more than other components like carbon steel. This type of alloy offers reliable protection from corrosion, eradicating the need for expensive maintenance and repair.


Corrosionpedia Explains Corrosion-Resistant Alloy (CRA)

Corrosion-resistant alloys are broadly used by various industries, especially those in chemical processing. These alloys provide reliable performance in the fields of health, energy, pharmaceutical, gas, oil and others. The use of these alloys promotes:

  • Excellent resistance to corrosion attack
  • Stress corrosion cracking (SCC) resistance
  • Ease of fabrication and welding

Generally, the move to make use of CRA should be conducted as early as the pre-engineering phase. For instance, these alloys are now widely employed in piping applications. Production technology and metallurgy have been established and constantly developed to let the utilization of corrosion-resistant alloys for extremely corrosive situations, like concentrations of hydrogen sulphine higher than 35%, temperatures reaching 220°C as well as pressure nearing 22,000 PSI.

For instance, in a sour system, alloys of molybdenum, like the alloy 625 consisting of 9% molybdenum, can handle severe conditions like the existence of elements such as free sulfur. Moreover, nickel plays a large role in the prevention of SCC when combined with molybdenum and chloride.

Choosing the right materials is crucial when using corrosion-resistant alloys. Some of the factors to consider include:

  • Ranges of alloy composition
  • Parameters of heat treatment
  • Complex material mixture metallurgy
  • Degradation mechanisms
  • Joining considerations

The proper selection of the right CRA for use in areas like transportation or production can be very complex. If this is not conducted properly, it could produce negative consequences. Therefore, all factors should be seriously considered.


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