Journal of Failure Analysis and Prevention

, Volume 5, Issue 6, pp 64–69 | Cite as

Mitigation of ammonia-induced SCC in a cupronickel alloy by additions of MgCl2

Part 1: Effect of chloride-containing solutions of sodium and magnesium on ammonia-induced SCC in a cupronickel alloy
  • D. C. Agarwal
  • S. Sarin
  • A. M. Bapat
  • S. Seshadari
  • R. Vishwakarma
Peer Reviewed Articles
  • 63 Downloads

Abstract

The authors carried out failure analysis of bent and branched copper-nickel alloy pipelines that had failed in marine environments. These failures were almost always dominated by a brittle stress-corrosion cracking (SCC) mode and could often be attributed to the presence of ammoniacal byproducts in the operating environment. Attempts were made to reproduce the marine-type field failures in the laboratory by testing a Cu-5.37%Ni alloy, similar to the material used in failed pipelines. The tests were performed under slow strain rate test (SSRT) conditions in aqueous ammonia and ammoniacal seawater. Results revealed that the ammonia-induced brittle SCC failures were predominant and reduced the load-bearing capacity of the alloy. The real-life failures are not simple SSRT-type failures. The operating conditions, in addition to the induced residual stresses from manufacturing/processing, subject the system pipes to external forces and widely varying pressures and fluid flow rates. This combination of stresses can produce both static and cyclic stress conditions, similar to a static load coupled with a low-amplitude cyclic load. Tests conducted under superimposed cyclic stresses on prestressed specimens were found to accelerate the stress-corrosion failures in the present copper-nickel alloy in an ammoniacal environment.

During the testing process, it was established that chlorides of sodium and magnesium also had a role to play on the ammonia-induced SCC. Further tests were therefore designed, and this paper summarizes test results, which point to the possible mitigation of ammonia-induced SCC in cupronickels by the addition of MgCl2.

Keywords

accelerated corrosion testing cracking behavior environmental failures environmentally assisted cracking failure mechanism magnesium mechanical property estimation 

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References

  1. 1.
    P.T. Gilbert: “Corrosion Resisting Properties of 90/10 Copper-Nickel-Iron Alloys with Particular Reference to Offshore Oil and Gas Applications,” Brit. Corros. J., 1972, 14(1), pp. 20–25.Google Scholar
  2. 2.
    D.C. Agarwal: “Effect of Ammoniacal Sea Water on Material Properties of Copper-Nickel Alloy,” Brit. Corros. J., 2002, 37(2), pp. 105–13.CrossRefGoogle Scholar
  3. 3.
    D.C. Agarwal: “Stress Corrosion in Copper-Nickel Alloys—Influence of Ammonia,” Brit. Corros. J., 2002, 37(4), pp. 267–75.CrossRefGoogle Scholar
  4. 4.
    D.C. Agarwal: “Effect of Ammonia Concentration on Environment-Assisted Failures in a Low-Nickel Copper Alloy,” Prac. Fail. Anal., 2003, 3(5), pp. 58–68.CrossRefGoogle Scholar
  5. 5.
    D.C. Agarwal and S. Seshadari: “Low-Nickel Copper Alloy—Role of Ammonia and Corrosion Retarding Media,” Proceedings of the 11th National Congress on Corrosion, Vadodara, India, July 17–19, 2003, e-Publication by NCCI, India.Google Scholar
  6. 6.
    Corrosion in Metals and Alloys—Stress Corrosion Testing—Part 7: Slow Strain Rate Testing, International Standard ISO 7539–7: 1989(E), pp. 1–4.Google Scholar
  7. 7.
    D.C. Agarwal: “Effect of Cyclic Stresses on the Stress Corrosion Cracking Behaviour of Copper-Nickel Alloy,” Corros. Eng. Sci. Techn., 2003, 38(4), pp. 275–85.CrossRefGoogle Scholar
  8. 8.
    ASTM Standard E-8, ASTM, Philadelphia, PA, 1992. Originally published as E-8-24T, last previous edition E8-90 under American Association State, Highway and Transportation Officials Standard, AASHTO No: T 68, pp. 130–45.Google Scholar

Copyright information

© ASM International 2005

Authors and Affiliations

  • D. C. Agarwal
    • 1
  • S. Sarin
    • 1
  • A. M. Bapat
    • 1
  • S. Seshadari
    • 2
  • R. Vishwakarma
    • 2
  1. 1.Institute of Armament TechnologyGirinagarIndia
  2. 2.c/o FMOMumbaiIndia

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