Saturday, October 29, 2011

India - Corrosion Effects - What is the limit of chloride in recirculating water having copper metallurgy?

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What is the limit of chloride in recirculating water having copper metallurgy? How does chloride attack on Copper and what is the limit we should maintain? Give some reference also.


Discussion posted by: Bhavesh Salve
Publication Date: 27 Oct 2011 

3 comments:

  1. Ashwini K Sinha • Dear Mr. Salvi,
    Copper metallurgy is used in seawater with around 35000 ppm chloride only thing is in such cases the copper tubes are passivated with FeSO4 layer (initially by direct dosing of FeSO4 subsequently it can be maintained by iron anodes or low dosage of FeSO4). Chloride corrosion can be controlled by azole based inhibitor. The attack by chloride is essentially by breakdown of passivation layer. Hope this answers your question. Ashwini Sinha
    19 hours ago

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  2. Manickam Valliappan • Corrosion of copper is influenced by many parameters - Temp, pH, Alkalinity, Sulfate, Dissolved Oxygen, Free Chlorine, Ammonia, Sulphide including Chloride. Since your interest is on recirculating cooling water type, combination of these factors should be taken into account to design a suitable operating window based on chloride limits. For instance,
    free chlorine concentrations were found to increase the dissolution of copper especially at lower pH. Some of the studies showed that the free chlorine decreased the corrosion rate of copper at a high pH of 9.3.

    How about the metallurgy of equipments that you are interested to cover? Is it pure Copper or Copper Alloys?
    1 hour ago

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  3. C.V.Srinivasan Chakravarthi Srinivasan • Bhavesh Salve Oct 29
    Copper piping failure is mostly caused due to pitting. Pitting leads to pin hole leaks.
    Copper pitting corrosion remains still poorly understood despite many research reports.

    Recirculating waters having high pH, low alkalinity, significant levels of chlordie and sulfate are known cases of pitting corrosion in copper piping. In some cases, aluminium, silica, total inorganic carbon and impurities in copper piping materials are also known to cause pitting.
    US EPA (environment protection agency) conducted a ten year pilot plant study. Essential result of pitting according to EPA study: Low dissolved inorganic carbon (DIC) - 5 to 10 mg C/L) at high pH (9) water in presence of Chloride (20 mg/L) was observed to cause pitting. at low pH 7 to 8 this did not occur. EPA study studied by products associated . Increasing DIC 10-50 mg C/L reduced pitting at high pH 9 or above

    You can find some general guiding information from GE Power & Water Water Chemistry Handbook Chapter 31 & Chapter 32 tables as general reference.
    Please note : Sources tried in US or Canada water chemistry may at best be a guidance and need not be suitable to Indian water chemistry related problems or for materials procured with impurities in copper metallurgy.
    If problems are related to recirculaing water in cooling tower or hot condenser tubes water chemistry in cooling tower viz., alkalinity, temp, pH, TDS, velocity etc will change to affect copper materials variedly.
    Hope this helps

    41 minutes ago

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