[MW:14472] RE: 14464] Sulphide Stress (SSC) and Chloride Stress Cracking (CSC) corrosion requirement

Hi Perumal,

It's not clear what're  the project technical requirements. However the testing requirements definitely indicate the intended application is for offshore. There are not many scopes of error in the offshore services.

As per the query posted below, the PQR on lower thickness i.e 3.05 mm would also require corrosion testing, as per the design basis specifications or clients's specifications.

One may use filler wires of same chemistry, same batch or  Lot No etc. But how abut the base metal ??? Does 3.05mm and 8.38 mm belong to the same heat No? If not then the corrosion resistance would not be the same.

I glanced though NACE TM-0177-2005.It looks like Method-B, i.e, Bent Beam method would be the most appropriate method for piping  of such lesser wall thickness.

I would think you need to discuss the issue with the Laboratory carrying out this test and your client and the independent(Third Party) inspector.

Let me know if it helps.

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net

-----Original Message-----
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of perumal govindan
Sent: Tuesday, June 05, 2012 12:43 AM
To: materials-welding@googlegroups.com
Subject: [MW:14464] Sulphide Stress (SSC) and Chloride Stress Cracking (CSC) corrosion requirement

Dear Experts,

Please clarify the below mentioned particulars,

we have carried out a SDSS PQR with 12" Dia. x 8.38mm thick, matl.
grade: ASTM A 928 Cl.1 (UNS S32760), thickness qualified range: 8.38mm to 16.76mm - carried out corrosion tests (like, pitting, crevice, chloride stress and sulphide stress), all physical and chemical tests are passed.

Hence for covering the thickness range, we have also carried out a PQR with 4" Dia. x 3.05mm, matl. grade: ASTM A790 (UNS S32750), qualified thickness range: 1.525mm to 6.1 mm. Here we got stuck up due to Sulphide stress (test as per NACE TM-0177)and chloride stress (test as per ASTM G-36) due to lower specimen thickness. As per NACE TM-0177 the minimum reqd. thickness for sulphide stress corrosion test is 3.81mm.

Now my PMC/Client is insisting to carry out the SSC corrosion test also in 4" Dia. x 3.05mm PQR test coupon. (Filler wire used: ER 2594, same batch & Lot Number used also in 12" Dia. x 8.38 mm)

Hence, kindly advise me that whether SSC test is required for the 4"
Dia. specimen or not.

Thanking You.

Govin

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