Corrosion in CRA pipes

[berry gamaliel]

Dear Experts 

In our project we are using CRA pipes, API 5L Grade B, thk- 35 mm. cladded with UNS00825  thk-5mm. 

Due to improper preservation of spools grinding and machining wastes deposited or setteled inside the spools and oxidation and corrosion started in a minor way. 

Please suggest whether chemical cleaning is required to to remove the minor corrosion or as it is a corrosion resistance alloy pipes will it withstand the corrosion. 

Another clarification too as it is a Corrosion resistance alloy why it cannot resist or prevent corrosion from grinding and machine wasted and during the service condition highly corrosive fluids will pass though it so how it will withstand that. 

Please clarify experts. 

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Regards

Berry Gamaliel

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Regards

Berry Gamaliel

[Alan Denney]

I understand that the designer has selected alloy 825 (as internal cladding) as adequate for the in-process service and you are asking why you have to remove swarf, from within the pipe. Since the swarf is from cutting a clad pipe it will be largely carbon steel. The reason is that the alloy 825 relies on a layer of passive surface scale to make it corrosion resistant. The swarf will set up a galvanic corrosion cell, assisted by the crevices formed under the corrosion product, the protective layer will be breached by the corrosion the surface will be pitted and corrosion can proceed in the pit regardless of what is done to the surface. I suggest you search for the terms, galvanic corrosion, pitting corrosion and crevice corrosion to understand the risks being created. The requirement that you prevent the ingress of swarf is correct.

 

Alan Denney

AKD Materials Consulting Ltd

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[dili...@gmail.com]

If the cladding has been contaminated by iron then you have to perform smooth grinding and pickling

Sent from my BlackBerry 10 smartphone.

From: berry gamaliel Sent: Κυριακή, 13 Μαρτίου 2016 - 05:57 To: material...@googlegroups.com Reply To: material...@googlegroups.com

Subject: [MW:24509] Corrosion in CRA pipes

[Ahmed Eissa]

Ni based alloy 825 is used to mitigate certain damage mechanisms, however fabrication of these alloy shall be performed with due care (similar to duplex and super duplex)  Please avail service data,  handled stream,  I suggest hydrocarbon with produced water or water injection service  A.E Material and corrosion engineer  Sent from Yahoo Mail on Android From:"berry gamaliel" <mechberr...@gmail.com> Date:Sun, 13 Mar, 2016 at 5:57 am

Subject:[MW:24509] Corrosion in CRA pipes

[Alan Denney]

Contamination by ferrous material of the surface of alloy 825 in a corrosive environment will result in breakdown of the protective layer on the alloy 825, pitting/crevice corrosion of the ‘more noble’ material, and for that reason contamination cannot be tolerated.

 

Alan Denney

AKD Materials Consulting Ltd

 

From: Ahmed Husain [mailto:ahm...@yahoo.com]
Sent: 13 March 2016 15:52
To: material...@googlegroups.com; Alan Denney <al...@denney1.freeserve.co.uk>; material...@googlegroups.com
Subject: Re: [MW:24517] RE: 24509] Corrosion in CRA pipes

 

As per my understanding, in galvanic corrosion, material listed lower in galvanic table is the one which should deteriorate. In this case, cs is the lower grade and should deteriorate, not the alloy 825. 

In all carbon steel piping, gasket winding and inner rings is normally SS, but there is no issue of galvanic corrosion.

I think, this issue of contamination should require more discussion.

 

Regards,

Ahmed

 

Sent from Yahoo Mail on Android

 

On Sun, 13 Mar, 2016 at 12:29 pm, Alan Denney

[Ahmed Husain]

As per my understanding, in galvanic corrosion, material listed lower in galvanic table is the one which should deteriorate. In this case, cs is the lower grade and should deteriorate, not the alloy 825. 

In all carbon steel piping, gasket winding and inner rings is normally SS, but there is no issue of galvanic corrosion.

I think, this issue of contamination should require more discussion.

Regards,

Ahmed

Sent from Yahoo Mail on Android

On Sun, 13 Mar, 2016 at 12:29 pm, Alan Denney

<al...@denney1.freeserve.co.uk> wrote: