Technology Research Of Measurement On Stainless Steel Corrosion Resistance

Stainless steel has many excellent properties, especially its good performance in corrosion resistance, which makes it have very broad application prospects.But currently,the market is filled with all kinds of stainless steel, of which the corrosion resistance is of varying quality. As a result, using scientific methods to measure and appraise various stainless steel corrosion resistance is an important task in the current application engineering of stainless steel.In this article, the corrosion resistance of four kinds of316stainless steel has been studied through electrochemical testing, metallographic analysis and chemical analysis in solution.Material corrosion potential and corrosion current can be obtained using Electrochemical test,which directly determines the material corrosion resistance. The non-metallic inclusions in the material are observed with optical microscope, which can determine the inclusions level of materials. The relationship between the inclusion and corrosion resistance can be found by combining the electrochemical tests, and after that, the corrosion properties of materials can be characterized through the non-metallic inclusions.After Stainless steel is soaked in3.5%NaCl solution continuing for some time, the corrosion resistance of stainless steel can be determined by measuring the content of iron ions in solution.Electrochemical test results show that the natural corrosion potential shares a close relationship with the corrosion resistance of material, and specifically, the more negative the natural corrosion potential is, the poorer the material corrosion resistance. The corrosion rate of materials can be calculated using material corrosion current density by Tafel curves characterization, and the change of the corrosion rate directly represents the corrosion resistance of materials. The measured corrosion current of the first sample in0.5mol/LH2SO4solution is0.633μA/cm2,and in3.5%NaCl solution that is0.549μA/cm2. But the measured corrosion current of the fourth sample in0.5mol/LH2SO4solution is0.131μA/cm2,and in3.5%NaCl solution that is0.123μA/cm2. Thus,we can conclude that the corrosion resistance of the first sample316stainless steel is the worst and the fourth is the best.Through the metallographic analysis we find that non-metallic inclusion content and distribution are different among the four kinds of316stainless steel,which has a direct impact on the corrosion resistance of materials:the more the inclusions are, the poorer the material corrosion resistance. It is found that the content of non-metallic inclusions in the first sample is the most, and the fourth is the least.In addition,we have determined that the corrosion resistance of the first sample316stainless steel is the worst through electrochemical test.Chemical analysis in solution shows that the corrosion properties of materials can be characterized through the change of iron-ions in solution after Stainless steel is corroded in the corrosive medium (3.5%NaCl),and specifically,the higher the iron-ion concentration is the poorer the material corrosion.The measured concentration of iron ions in the first solution is0.597μg/L; that in the fourth solution is0.187μg/LIt is further proved that the corrosion resistance of the first sample316stainless steel is the worst and the fourth is the best.All the above experimental results have also proved that the electrochemical measurement methods, metallographic analysis and measurement of iron ions concentration in solution can be an efficient way to characterize the corrosion resistance of materials. what’s more, the results are coincident.