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what is the impact on material to increased chloride level 200 to 230PPM in 50% caustic,

  • 1.  what is the impact on material to increased chloride level 200 to 230PPM in 50% caustic,

    Posted 19 days ago
    process- Membrane 50% caustic,
    Maximum operating Temperature- 40c
    Issue happened: crude membrane caustic produced higher sodium chloride residuals, which increased 200 ppm to 230 ppm  sodium chloride in 50% caustic,
    Metallurgy involved, Piping ss304, Tank carbon steel sa 283,

    let i need expert opinion, what is the impact of higher chloride on  piping and  tank Material of construction,

    Thanks,

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    AAMIR SADDIQ
    STATIONARY ENGINEER
    SABIC
    JUBAIL
    00966133574273
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  • 2.  RE: what is the impact on material to increased chloride level 200 to 230PPM in 50% caustic,

    Posted 18 days ago

    Chlorides in caustic soda solution do not cause chloride SCC of austenitic stainless steels. A solution of 0.5 g/L NaOH at pH 12 is sufficiently alkaline to avoid this type of cracking that is common in neutral or acidic solutions. It has also been shown that chlorides inhibit caustic SCC. Mercury cell caustic typically contains 20 to 30 ppm chlorides, while diaphragm cell caustic is more likely to contain up to 1% chlorides. While chloride-contaminated caustic soda solution may not cause SCC of austenitic stainless steel if the caustic soda is consumed, for example, in a neutralizing process, the residual neutral chloride containing solution may then initiate cracking.  This level of chlorides at 40C is unlikely to cause corrosion or cracking of carbon steel.

     



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    Mike Davies
    Nickel Institute
    Powys
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