Abstract
Stainless steel alloy SS-304 is widely used in many engineering applications primarily for its excellent corrosion resistance, ease of fabrication and aesthetic appeal. Many kitchen appliances are made from SS-304 alloy because of its durability, ease of cleaning and beautiful finish. However, over the years of continuous usage and cleaning by detergent bar and abrasive clothes the initial brightness and shine of the plates and dishes undergo considerable degradation. In this work, we report the results of a thorough investigation of the physico-chemical characteristics of the surface regions of both new and old SS-304 plates of known history of continuous usage to identify the key physical and chemical factors that are responsible for the loss of shine. Several analytical techniques viz. SEM/EDX, AFM, XPS, XRD, Reflectance FTIR, Profilometry and Reflectance spectrometry in the visible region have been used for experimental investigation of surface structure, morphology, roughness profile, chemical composition and appearance measurements of several steel samples. In addition, glossmeter has been used to measure the gloss of the samples at certain specific angles. It seems that surface roughness is one of the key physical parameters that play an important role in the reduction of brightness and shine. The other parameter is the presence of a thin surface film on the steel surface. In order to analyze the experimental data and to predict the shine and brightness phenomena quantitatively, we have used Fresnel’s theory to compute first the reflectance from each component of SS-304 alloy assuming it to be a smooth surface and then extended it to compute the reflectance of the alloy surface (SS-304). In order to interpret the reflectance from old and used plates, we have further used Beckmann’s theory of light scattering from random rough surface to analyze and predict the appearance aspects of the alloy surface quantitatively. Both the experimental and computed results show good agreement, thus validating the reflectance model used for computing the reflectance from SS-304 alloy surface and the appropriateness of Beckmann’s model of random rough surface.
Highlights
Stainless steel is one of the most important and widely used engineering materials primarily for its excellent corrosion resistance and beautiful aesthetic appeal
Comparison of lattice spacings (d values) and relative intensities (I/Io) of the three samples with the Austenitic SS samples indicates that SSPN has essentially identical d values, there is some deviation in the relative intensity, which might be due to the different levels of impurities present, and due to absence of Mn in the standard used for comparison
Supportive evidence can be obtained from the roughness data given by the profilometer, which clearly shows that there is a six-fold rise in surface roughness from the new panels (0.025 μm) to the old plates (0.153 μm)
Summary
Stainless steel is one of the most important and widely used engineering materials primarily for its excellent corrosion resistance and beautiful aesthetic appeal. In addition to its various engineering applications, stainless steel has gained popularity as a material for kitchen appliances and utensils due to economic reasons, aesthetic appeal, excellence in corrosion resistance, and durability. Physical and chemical factors that are responsible for the initial shine or gloss of the alloy surface, and the mechanism of degradation of shine with time and usage. For this investigation we have used both experimental techniques and theoretical modeling of reflectance from smooth and rough surfaces to understand the appearance aspects of different samples. In addition we have used XRD for phase analysis of stainless steel samples and profilometer and glossmeter for the measurement of surface roughness and gloss values at different angles, respectively
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