CORROSION PROBLEMS WITH SUBMERSIBLE PUMPS C076

CORROSION PROBLEMS WITH SUBMERSIBLE PUMPS C076 

  • Cast iron pumps solves most submersible pumping operations. This normally presents no corrosion problems when pumping liquids such as surface water and domestic sewage. The low oxygen content in raw sewage lowers its corrosion effect to almost nothing.
  • Stainless steel is sometimes used as the main material in submersible pumps for two reasons:
    • Corrosion resistance in acidic liquids
    • Where the purity and color of the liquid being pumped is critical.
  • A less expensive and more flexible alternative against salt-water corrosion is to use a protective coating on a conventional cast iron pump. The most widely used coating is ceramic epoxy (a polymer material). Normally, zinc anodes are used in conjunction with ceramic epoxy coating because of the inevitability of abrasions and scratches occurring in the coating.
    • The thermal coefficient of expansion of most plastics is several times that of cast iron, so watch out for separation at elevated temperatures.
  • The use of sacrificial zinc anodes significantly extends the life of a coated pump. Between five to ten anodes are implanted at various points around the cast iron structure of the pump.
    • An alternative to using sacrificial anodes is to supply the micro current by cable from an external power source. This is known as an “impressed current.” In this method, a non-sacrificial anode is suspended in the liquid beside the pump. The anode is attached by cable to the pump and the micro current is introduced into this cable. The impressed current method, however, is complicated, expensive and requires a lot of monitoring to be effective.
    • The extra cables required become obstructions in the pump well and often get damaged.
    • The implanted (sacrificial) anode method, being simpler and less expensive, is normally preferred.
  • Chlorinated rubber is often used to prevent corrosion of cable sheathing for conventional pumps.
    • Fluorinated ethylene plastic is an alternative coating material

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  • On February 15, 2018