Erosion (?) into a seawater pipe 1

[MaxNeg63]

Dear All, we've received for analysis a CS forged spool (about 16" diameter) used to connect a butterfly valve to an heat exchanger. The H.E. is used to cool process water using seawater as cooling medium: into the forged pipe flows seawater that goes into the H.E.
The internal surface of the spool is completely white (bright) and has the same appearance of the sea surface view from high above. Could it be erosion? If so which could be the possible cause since the butterfly is always open and there's no sand into the water? Could the hardness of the forged item have any influence?
Thanks for the help

 

[Goahead]

It is difficult to perform a material investigation based only on color without a reference. If you grind lightly with sand paper a small area, you will be able to determine if the color changes, or if it is on the surface the same that in bulk. Could you try to collect from the surface small flakes and send them to analysis? Could you examine the surface with a microscope and see what happens when you try to scratch it?

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

 

[MaxNeg63]

Sorry Goahead, I didn't explained well the look of the surface: it is absolutely free of rust, unoxidated. So the surface has no layer to be scratched but you can see only bright metal.
Hope this help
Best regards

 

[mshimko]

If the surface appears smooth, its not erosion.

Are you sure it's carbon steel? Is a magnet attracted stongly, weakly, or not at all?

 

[MaxNeg63]

No, the surface is not smooth but kind of corrugated (like a rough sea seen from above). I'm sure it's carbon steel because I've seen the manufacturing data

 

[EdStainless]

What is the flow velocity? My guess is erosion/corrosion. Is there any Cr in the alloy?

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[SMF1964]

I would also consider cavitation as a possibility, especially if this spool piece is immediately downstream of the valve.