Martensitic stainless steel apperaence due to rust

[metboss]

Good day everybody,

We have carried out the visual inspection of 13%Cr pipes (L-80 13%Cr/AISI 420, API 5CT) and outcome had reveled rusty appearance on entire body. Upon asking, vendor informed that pipes were kept outside in open yard and due to unexpected raining; it was exposed and resulted in rusting (like black scale appearance) on external surface.
To know the genuine reason, what all can be instructed to vendor?

I have advised them to proceed with following steps:

1)PMI (positive material identification) to be carried out to know the chemical composition (13%Cr or not??)
2)Sweep blasting to be done to confirm bright & shiny appearance of surface
3)Coating to be applied on final product i.e. drilling cross-overs size: diameter 3-1/2” length 6 Ft

Do you have any suggestion any apart from above? And, also please can somebody suggest me on common appearance of 13%Cr steel (bright or??) AND
type of coating/painting applied on 13% Cr material?

Thanks in advance....

 

[BobBollards]

Hi, the appearance depends on how the pipes where made, it should say on the material certificate eg "hot rolled" or "descaled" this will affect how they look


Bob

http://www.metals4u.co.uk

 

[EdStainless]

surface rust on 13Cr is not uncommon.
If the material has been pickled it may look whiter and not rust as easily, but it still is only 13Cr.
Blasting will make it look better for a while, but unless you follow with chemical passivation you will get surface rusting again fairly quickly (if you have much humidity).
Usually the surfaces are left bare, and if they rust a little so be it.

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Plymouth Tube

 

[metboss]

Good day,

Please refer to attached photgraph and advise your comments on visual condition of Pipe. And, also advise on proposed coating for 135Cr material.

Regards

 

[metboss]

Thanks bobbollards and edstainless for your comments..

Is ferrite test using ferrito-scope applicable to martensitic stainless steel(AISI 410/13%Cr)? Can we suggest this test to assess contamination?

Regards

 

[blacksmith37]

Quick check on alloy : On a clean , bright spot, put a drop of conc. nitric acid; there will be no reaction on 13Cr. L-80 13 Cr is not necessarily the same as any AISI grade.
I would blast clean and oil, then keep dry. I have seen L80 13 Cr rust because it was stored in a plastic bag (and got wet).

 

[EdStainless]

1. Does the rust hurt anything? In most cases it is purely cosmetic.
If you want to blast, acid clean, rinse and oil, then they will stay nice looking.
2. You cannot use magnetic measurements since this alloy is fully ferromagnetic.

I don't think that there is anything wrong. It is 13Cr, it rusts.

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Plymouth Tube