selecting Proper storage tank material - Advise

[Raafat]

Dear Gents,

Kindly support selecting the proper storage tank material of Sodium Polycarboxylate.

currently, I have 100 ton CS storage tank of  Sodium Polycarboxylate the internal Stainless steel 304 cladding 2mm sheets.

After one year of operation, we found corrosion spots and  Sodium Polycarboxylate leakages.

internal SS 304 cladding welding joints by Argon welding - 7018 welding wires.

tank tested by water and it was excellent without any leakages.

The  Sodium Polycarboxylate data sheet is attached.

I've attached photos of the corrosion.

Please advise which material I should select to fabricate a storage tank for  Sodium Polycarboxylate and how to solve current corrosion spots.

thanks. 

[Ahmed Eissa]

Dear,

I can see that corrosion is limited only to the weld joints. If yes, then why 7018 is used for welding. 7018 is carbon steel (CS) filler and shall not be used with SS cladding in case service is corrosive otherwise galvanic corrosion will occur.

Usually the chemical MFR issue detailed MSDS where it list compatible and non-compatible material for material handling and storage. Go ask him and if CS is not suitable for the stored material inside tank, then it is mistake from tank manufacture. In simple word, if you selected internal clad of SS, then internal welds exposed to service also shall be SS not CS.

also, I can see localized corrosion which may be either 1 - wrong welding electrodes only for these welds or Improper pickling and passivation after fabrication before placing tank in-service

thanks
Ahmed
Corrosion Engineer

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[Awais ali]

Hello Everyone,

Could you please advise and share your experience regarding SPWHT requirements of material (Plate, Pipe, forging, Fittings and Flanges) for pressure vessels as per ASME and ARAMCO standard. and please elaborate in detail and also mention the reference if possible. 

If you require any further information, please do not hesitate to contact me .

Thanks & Best Regards,

 

Awais Butt

Senior QA/QC Inspection Engineer | QA/QC Department