Copper added alloys 2

[maintennance]

In one of the process document it has been indicated that the copper and the copper added alloys shall not be used in Wet H2s environment.One vendor has quoted for 17-4PH material for the shaft sleeve which contains 4 % copper. Why cu shall not be used for H2S environment. Thanks to clarify

 

[desertfox]

Hi maintenance

Possibly Stress Corrosion Cracking.

desertfox

 

[desertfox]

Hi again

Have a look at this article:-

http://www.npl.co.uk/upload/pdf/stress.pdf

desertfox

 

[maintennance]

Thank you very much desertfox for your valuable article .

 

[desertfox]

Hi maintennance

Your welcome

 

[cloa]

Though why anyone would group together copper and copper added alloys does not make any sense. What magical property does copper have alone and as an alloy addition that makes it special? High Strength precipation hardened steels have more in common (particular SCC) than the particular alloy addition to make it PH.

 

[TVP]

ISO 15156-3 allows the precipitation hardening stainless steel 17-4PH (UNS S17400) to be used in H₂S environments provided that the maximum hardness is 33 HRC, and that it has been heat treated using an precipitation-hardening cycle at 620 C (1150 F) for 4 hours minimum. I think that the "copper added alloys" comment was probably just someone's particular choice of words, and probably meant copper-based alloys, not those that contain small alloying additions of copper.

 

[redpicker]

I agree with TVP.
It sounds to me like a translation issue, where "copper-based" got translated to "copper-added".
17-4PH in the DH1150 condition has been used for decades in H2S environments and is specifically listed in ISO 15156-3 in this conditon.

rp

 

[TomEun]

Definition of copper based alloys (Cu> 50%) and copper added (containing/bearing) steel (Cu + alloy elements < 50%) is important to recognize the restriction in wet sour service.

[Copper Alloys]
- The copper alloys, such as 90/10 Cu/Ni or 70/30 Cu/Ni, are acceptable in NACE MR0175. However the corrosion rate may be high in wet sour service if dissolved oxygen is present. Some oil producers have an experience of Galvanically Induced Hydrogen Stress Cracking in copper alloys.
- In sour service containing NH3 (amine, ammonia, salt deposit environment, etc.), brass and bronze shall not be used. The use of Monel (70Ni-30Cu), 90/10 Cu/Ni or 70/30 Cu/Ni should be also avoided because the service can lead to rapid corrosion and possible SCC.

[Copper Containing/Bearing Steels]
- NACE MR0175/0103 allow use several steels including 17-4 PHSS (< 33 HRC). However, in sour service containing NH3 (amine, ammonia, salt deposit environment, etc.), copper containing steels should be avoided except a trace copper (< 1%) containing steel to promote SSC resistance. 0.2-0.3% copper containing steel has greatly improved the HIC resistance.
- Many oil producers are using 17-4 PHSS only for valve stems, shaft, sleeve bearings, thrust bearings and mechanical seal throttle bushings in pumps and compressors which are required high strength in wet sour Service without NH3.

Thomas Eun

 

[metengr]

Yes, indeed there are copper-containing steels. Excellent post above.

 

[TemperedMartensite]

Alloy 925 contains over 2% Cu and it is used extensively in sour environments. I will say that 17-4 and K500 have a bit of dubious history - but that is due to the alloy and not the copper add.