Metal finishing Q&As since 1989

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SS316L welding corrosion

Hello everyone,

I've got a problem of pitting (localized corrosion) on all the weldings of an industrial plant. The trouble is that all the corrosion is localized on pipes of raw water line. We have a demineralized water plant for a cycle. We have RO and RO+EDI to produce 18 MOhm water quality. But our problem is the raw water. All the welding of raw water line has a little pitting process so we are thinking about the chlorides, but our maximum concentration of chlorides are 200 ppm of Cl- (as chloride), so we don't understand if the real problem is chlorides or perhaps other ions that are improving the local corrosion on the welding.
We are interested on which is the maximum concentration of chlorides that a SS could stand on normal conditions, we are talking about 25 °C, raw water treatment (brackish water).

Thank you for all.

Pla Joaquin
product designer - Madrid, SPAIN
September 2, 2009

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September 14, 2009

dear sir.
you have to use only demineralized water for your application. you can have a demineralized water treatment near by and only feed the demineralized /or buy demineralized water from suppliers which is not very costly compare to your equipments getting corroded. demineralised water only to your required system. other wise this problem will continue for ever. even a very small percentage of chloride will spoil all you equipment.

with warm regards.

B. Manickavelu
- Bangalore, India

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Did you passivate the welds? This is necessary.
Is the chorine in the form of chloride ions or chlorine? Chlorides are very bad, chlorine dissolved is not as bad.
What kind of weld did you use TIG, MIG?

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

September 17, 2009