Characters Of Electrochemical Noise Of 304NG Stainless Steel In SSRT Test In Acidic Sodium Chloride Solution

Nuclear power materials are under high temperature and pressure, irradiation and other adverse working conditions for a long time. And corrosion of nuclear power materials threatens the safe operation of nuclear power. As a common form of localized corrosion, Stress corrosion cracking(SCC) is always unpredictable and causes great damage, so it should attract people's attention.304NG stainless steel is a common nuclear power material. So it is very important to study early crack initiation signal of SCC for making good preparation for on-line monitoring of nuclear power materials. Electrochemical Noise(EN) technique is in situ and nondestructive.And it can provide much information about the process of corrosion and the important basis for studying the corrosion process and mechanism. Now, many scholars have already study SCC of nuclear power materials by EN technique. But there is still little research on on-line monitoring of nuclear power materials.In this paper,it is detected that 304NG stainless steel occurring SCC in acidic sodium chloride solution during Slow Strain Rate Test(SSRT) and Constant Load Tensile Test, some follow studies have been done by electrochemical noise technique and acoustic emission technique. The result showed that SCC occurred quickly. Corrosion forms of 304NG stainless steel develop gradually from localized corrosion which is SCC and pitting to complicated general corrosion which include development of crack and pitting. In Constant Load Tensile Test,potential - time, and current density - time curve of four samples with different stress values are both similar to samples in SSRT. By the change of the slope of both total energy—time and total counts—time curve, it can be distinguished that different stages of corrosion development. In this paper,it is also detected by potential noise technique that 304NG stainless steel, which is precasted to get a gap, both in the heating process of the autoclave and in water under high temperature and pressure during SSRT by the potential sensor which is made by Laboratory. After SSRT, there are some cracks on the sample surface because of tension. These cracks are not stress corrosion cracks.