Stainless Steel Point Corrosion Failure Analysis
Abstract
Stainless steel is a very popular and versatile material in many industries. It is used for various applications due to its corrosion resistance, strength and low cost. However, due to its alloy composition, stainless steel is susceptible to localized corrosion, which can lead to corrosion failure at points of stress concentration, such as welds, joints, fasteners, etc. This paper presents a corrosion failure analysis of a stainless steel point using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX); and Focused Ion Beam (FIB). The points examined were of different shapes and sizes, and all had suffered uniform corrosion. The results of this study will provide a better understanding of how localized corrosion can lead to failure, and aid in the design of components with increased corrosion resistance.
Keywords Stainless steel, corrosion, point failure, SEM, EDX, FIB
1. Introduction
Stainless steel is an austenitic stainless steel consisting of a mixture of iron, chromium, nickel and other alloying elements. It has high corrosion resistance, strength and low cost, making it widely used in many industries. However, stainless steel is susceptible to localized corrosion and pitting, as its alloying elements can become depleted in localized areas due to corrosion. This can lead to corrosion failure at points of stress concentration and welds, joints, fasteners, and other areas. In order to design components with improved corrosion resistance and strength, it is necessary to understand the corrosion failure mechanisms at stainless steel points.
2. Experiments
In this study, several stainless steel points were prepared for the corrosion failure analysis. The points were cut from round stainless steel tubes of different sizes. They were then sandblasted to a uniform surface finish, and the points were chromated to improve corrosion protection. The points were then installed in an environmentally-controlled chamber and exposed to a salt spray environment. After the exposure period, the points were examined using SEM and EDX , to analyze the morphology and composition of the surface, respectively. The surface of the points was further characterized using FIB , which was used to prepare the specimen and to obtain high-resolution imaging and elemental composition analysis.
3. Results
The results of the SEM and EDX analysis revealed uniform corrosion on the surface of the points. The corrosion rate increased with increasing exposure time in the salt spray environment. The results of the FIB analysis revealed a uniform corrosion pitting mechanism, with small pits distributed over the surface of the points. The concentration of the pits was found to be higher at points of stress concentration, such as welds, joints, and fasteners. The FIB analysis also revealed the presence of corrosion products (oxide scales) on the surface, which further contributed to the corrosion resistance of the stainless steel points.
4. Discussion
This study has analyzed the corrosion failure of stainless steel points exposed to a salt spray environment. The results of the SEM and EDX analyses revealed uniform corrosion on the surface of the points, with the corrosion rate increasing with exposure time. The FIB analysis revealed the presence of uniform corrosion pits distributed over the surface of the points, with higher concentration at points of stress concentration. The presence of corrosion products on the surface further improved the corrosion resistance of the stainless steel points.
5. Conclusion
This study has presented a corrosion failure analysis of a stainless steel point using SEM and EDX ; and FIB . The results of this study provide a better understanding of how localized corrosion can lead to failure, and aid in the design of components with improved corrosion resistance and strength.
