Influence Of Water Chemistry On Corrosion Behavior Of304Stainless Steel In High Temperature-high Pressure Solution

The failure of the key components of nuclear power plant equipmented in theservice environment of high temperature and pressure will lead to nuclear powerequipment accident, giving rise to the issue of nuclear safety.Therefore,the study ofthe electrochemical behaviors of the structural materials of nuclear power plant inhigh temperature and high pressure aqueous solution is particularly important.Thispaper mainly introduced the influence of water chemistry on corrosion behavior of304stainless steel in high temperature and pressure water.The corrosion behavior of304stainless steel in high temperature and pressureconditions tested by electrochemical noise method.The electrochemical noise sensorwhich was used in high temperature and pressure aqueous solution was produced.In this paper,the corrosion behavior of304stainless steel in different temperature(27℃、100℃、150℃、200℃、250℃) conditions was investigated by electrochemicalnoise sensor.The results indicated that with the temperatures increase,the corrosionoccurred on the304ss,from the standard deviation of current noise we can see that inthe high temperature, corrosion rates of304ss speed up.And with temperature andpressure increase,electrochemical noise resistance declined.So it can be concludedthat304ss had been seriously eroded under250℃.By means of the metallography andSEM, it was not difficult to see that304ss surface was oxidized and there arecorrosion products on the surface of304ss after immersed in the autoclave.The paper also studied the influence of Zn on the corrosion behavior of304ss inthe high temperature and pressure buffer solution.Electrochemical noise tests wasperformed and the test temperature was27℃、100℃、150℃、200℃、250℃respectively.The results indicated electrochemical noise resistance changed in a stablerange,and the standard deviation of current noise becomed a relatively stable valueand the standard deviation of current noise was the highest in250℃.So we canconcluded that the corrosion of304ss was not very serious and corrosion rate is thehighest in250℃.Compared with the first group of experiment (without Zn),thestandard deviation of current noise is lower,and the electrochemical noise resistancebecome higher.Morphologies of surface oxide films were investigated, the surfaces of304ss were mainly covered with loose particle-like oxide flms.The results indicatedthat Zn addition can improve corrosion resistance of304ss in the high temperature and high pressure conditions effectively.The paper also studied the influence of Cl-on the corrosion behavior of304ss inthe high temperature and pressure buffer solution.Electrochemical noise tests wasperformed and the test temperature was27℃、100℃、150℃、200℃、250℃respectively.Compared with the first group of experiment (without Cl-),theelectrochemical noise resistance is very low,the surface protection performancereduced.From the metallographic figure we can see small corrosion pit on the surfaceof sample.So the results indicated that with temperature and pressure increase,thesample presents pitting corrosion because of the Cl-.