Corrosion Reason of the Shaft of a Charging Pump in a Nuclear Power Station

Localized corrosion was found on the rotation shaft of a charging pump after decontamination. In order to find the reason of localized corrosion, examination of charging pump and simulation experiment were carried out. The results showed that crevice corrosion happened on martensitic stainless steel when the decotanmination process was taken inappropriately. The self corrosion potential of martensitic stainless steel was lower than that of austnitic stainless steel, which could accelerate the corrosion rate of the shaft due to galvanic corrosion. The corrosion reason of the shaft was due the co-effect of crevice corrosion and galvanic corrosion.