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.