Abstract
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.
Highlights
Film-forming amine (FA) is a specific chemical which can form a hydrophobic layer on the metal surface in liquid or vapor phase
Comparing the same sample exposed to the test environment and exposed to the inert environment, the farther the ratio deviates, the higher the cracking sensitivity
The test results show that the fracture absorption energy of the sample is basically the same in FA and non-FA environments, so the FA used in the test will not significantly affect the SCC behavior of TP 439 stainless steel and 690 TT alloy under slow strain rate conditions within the test concentration range
Summary
Film-forming amine (FA) is a specific chemical which can form a hydrophobic layer on the metal surface in liquid or vapor phase. This type of chemicals usually contains a primary, secondary, or tertiary amine structure (or a combination thereof) linked to a hydrocarbon chain, usually with more than 10 carbon atoms, such as octadecylamine and oleyl-1,3-propanediamine. In the thermal power industry, the utilization of FAPs into implementing medium- and long-term boiler maintenance after shutdown has become one of the main maintenance methods [1, 2]. The operating experiences of many thermal power plants showed that the shutdown protection of FAPs can effectively reduce the corrosion rate during the shutdown period. The unit has the following advantages after startup: water quality qualified time is shortened and start-up time is shortened
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