Re: [MW:20198] Corrosion in Super Duplex Stainless Steel - Sea Water

Hi.

Duplex stainless steels have a good resistance to atmospheric corrosion as well as chloride corrosiin cracking.

But these steels are prone to form intermetallic compounds like sigma, chi.. These componds drastically reduce pitting resistance of duplex steels.

Sigma phase is a iron chromium compond (50-50). It reduces chromium levels in grain boundary areas and make steel susceptible to pitting.


It seems in your case also this is true. During welding of duplex steel you have encountered the temperature range in which these phases form.





On Friday, February 28, 2014, José Luís Ferreira <jluis.nf@gmail.com> wrote:
> Dear experts, 
> In my project, we're in trouble corrosion (pitting) in pipes SDSS (UNS S32750 / UNS 32760), the base metal is SDSS (UNS S32750 / UNS 32760), the fluid is seawater. Attached photos showing the defects. I would like someone to help me with technical information about the mechanisms that cause such defect, how to avoid and correct. 
> Regards,
>
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