Corrosion of 487-2C on production platform

[ghazelip]

I'm looking for reasons why a 487-2C material would corrode with only slightly lower Ni,Cr,Cu content than an adjacent item. Both meet ASTM requirements for proper classification. 487-2C has no lower bounds for these alloying elements. An item with .09Cr,.09Ni,.16Cu Wt% corroded within one week in a sweet crude environment, prior 487 item had a 20 year history. A mill coating or machine fluid has been speculated, but no evidence.

 

[Goahead]

If the difference in behavior cannot be speculated, would it not be worth to launch a complete metallurgical investigation?

http://www.welding-advisers.com/

 

[EdStainless]

Small diferences in Cr may have an impact, but my money is on either microstructure (thermomechanical history) or surface condition.

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