Sustainable Construction A Life Cycle Approach in Engineering

• When subjected to high concentration of chloride ions (sea water) and elevated temperatures,
localized severe corrosion known as pitting corrosion can occur. Besides, stress
corrosion cracking is a severe form of stainless steel corrosion that appears under tensile
stress (service loads or residual stresses) and corrosive environments. But this
mode of corrosion applies only to austenitic stainless steels and depends on the nickel
content.
3.2 The 304, 316 and 430 grades
Table 2. 304, 316 and 430 stainless steel grades main mechanical properties.
304 316 430
Ultimate strength (MPa) 520 520 450
Yield strength (MPa) 210 220 205
Maximum elongation (%) 45 40 22
Modulus of elasticity (GPa) 200 200 200
Austenitic type 304 (namely 1.4301 in euronorm, 18/8: 18% chromium and 8% nickel) has excellent
corrosion and is highly ductile which makes it used for sinks and saucepans. This grade
is usually available in the following forms: sheet, plate, welded mesh, bar, pipe, decorative tube
etc. The 316 type (1.4401), containing an addition of molybdenum, has improved corrosion resistance.
It is usually regarded as the marine grade. This grade is nevertheless prone to pitting
and crevice corrosion in warm chloride environments and subject to stress corrosion cracking
above 60°C. High chromium content ferritic grade 430 (1.4016) combines intermediate (good)
corrosion resistance with good formability and ductility. The corrosion resistance is optimal if
the surface is highly polished. It can be obtained as bright annealed, polished sheet, square, rectangular
and round tubes etc.
3.3 The surface finishes and Solar Reflectance Index
An extremely wide amount of surface finishes is available. In (Cochrane & Helzel 2005), additionally
to the description of the standard mill finishes and mechanically treated surfaces finishes
provided in EN10088 part 2, technical advice on their applications are also provided. The description
of the surface finishes is nevertheless out of the scope of this paper.
It was previously mentioned that scoring systems such as LEED promote the use of “cool” surfaces
to increase the thermal performance of buildings as well as decrease the urban heat island
effect. To determine the effect of the reflectance and emittance on the surface temperature, the
Solar Reflectance Index (SRI) is used, it varies from 100 (for a standard white surface) to zero
(for a standard black surface). The higher the SRI, the cooler the surface remains. SRI incorporates
both the emittance and reflectivity of the surface in a single value. Emittance, also known
as emissivity of a surface, is a measure of the surface capacity to emit heat, it ranges between 0
and 1. Most opaque non-metallic materials encountered in the built environment (such as concrete,
masonry, and wood) have an emittance between 0.85 and 0.95. Whereas stainless steel
emittance can range from 0.85 to less than 0.1 (highly polished stainless steel) depending on the
surface finish (Qian et al. 1996). Moreover, smooth, bright metallic surfaces will be characterized
by directional reflection of light (low roughness, low dispersion) while ceramic (high
roughness, high dispersion), for instance, will be characterized by a diffuse reflection (Koch,
2001). For stainless steel, to a mirror finish will correspond a high reflectivity, to a matt-rolled
finish will correspond an intermediate reflectivity and to a patterned finish will correspond a
low reflectivity. Alternating stripes of matt and mirror polished finish can also be used to control
this parameter. It is thus possible to recommend the finish, depending on the application, to
control the SRI. Of course, stainless steel has a role to play if high SRI is required (“cool” surface)
but it might also be detrimental to comfort (dazzling of pedestrians) or security (air or road
traffic applications) and, in these cases, a matt patina should be advised.
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