Purpose
The purpose of this paper was to study the corrosion control of B10 copper-nickel alloy using the LiOH-N2H4 compound inhibitors and to evaluate the feasibility of replacing the original inhibitors (NaNO2-Na2MoO4) with the new ones (LiOH-N2H4) for the chilled water system in a nuclear unit.
Design/methodology/approach
The corrosion resistance performance of B10 copper-nickel alloy was evaluated during the whole replacement process of inhibiters using electrochemical tests and surface analysis techniques.
Findings
The results indicated that the corrosion of B10 copper-nickel alloy could be prevented effectively using LiOH to increase the pH value of solution higher than 10.0 and using N2H4 to consume dissolved oxygen. During the replacement process of inhibitors from NaNO2-Na2MoO4 to LiOH-N2H4, the corrosion resistance performance of B10 copper-nickel alloy had not decreased greatly. The new LiOH-N2H4 inhibitor, which could enhance the compactness of rust, was able to reduce the corrosion rate of rusted B10 metal.
Originality/value
It is feasible and operable to replace the NaNO2-Na2MoO4 inhibitors with the LiOH-N2H4 inhibitors for the corrosion prevention of B10 copper-nickel alloy. The research results can provide guidelines for the inhibitor selection of chilled water system in a nuclear unit.
Film-forming amines have been widely used in thermal power plants for maintenance after shutdown, and there are more and more applications and researches in nuclear power secondary circuits for this purpose. However, in the direction of stress corrosion cracking, there is not much research on the influence of film-forming amines on metal materials. This article uses the high temperature slow strain rate test (SSRT) method to evaluate the influence of a commercial film-forming amine on the stress corrosion cracking behavior of two conventional island materials for PWR nuclear power plants. These two metal materials are the heat exchange tube materials of the high-pressure heater and steam generator in the high-temperature operation area of the secondary circuit of a nuclear power plant: TP 439 stainless steel and 690 TT alloy. The test analyzed the mechanical properties and fracture morphology. The test results show that in the test concentration range (<5 mg/kg), the film-forming amine will not affect the SCC of TP 439 stainless steel and 690 TT alloy under the condition of slow strain rate. The behavior has a significant impact. In practical applications, the general dosage of film-forming amine is 1-2 mg/kg. This data is lower than the film-forming amine concentration used in the experiment. Therefore, there is no need to worry about the obvious impact on the SCC behavior of TP 439 stainless steel and 690 TT alloy.
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