Stainless steel is selected for architectural application, for their corrosion resistance and potential aesthetic appearance. For internal applications other factors also important, including: – Risk of the fingermarking from contact with ‘human traffic’ (on wall cladding and lift panels) risk of scratching or staining from contact with glasses or drinks (bar tops) can routine cleaning be expected to maintain the surface appearance but not cause any unacceptable changes in appearance
Selection of stainless steel grade
With the exception of harsh internal environments often encountered in leisure and hydrotherapy pool buildings, grade selection is not a critical factor. For most building interiors intended for human occupation, either the ferritic 430 (1.4016) or austenitic 304 stainless steel can be considered.
Depending on surface finish, there can be slight natural colour differences between them, which could influence the choice. The ferritic steel can have a blue tinge, whilst by comparison, the nickel containing 304 stainless steel has a slight yellow tinge.
Surface finishes
There is a wide range of possible finishes. Normally ‘ex-mill’ finishes, with the exception of the bright annealed, 2R finish, may not be considered as aesthetically suitable as textured, polished and coloured finishes.
British Standard EN 10088-2:2005 defines these basic ‘special’ finishes in table 6. Specifying finishes to EN 10088-2. The finishes include: Patterned, Corrugated, Mechanically Polished or Brushed, Coloured
Mechanically polished or brushed finishes
This includes a wide range of possible finishes, including designations ‘G’, ‘J’, ‘K’ and ‘P’ of EN 10088-2.
Brushed finishes may be better choice than ‘ground’ or ‘polished’ for preventing fingermarking.
As the austenitic 304 stainless steel is not particularly hard, highly polished surfaces can be susceptible to damage. Where surface scratching is very likely on bar or counter tops, then a uniform (non-directional) polish may be better than directional finish. Unless contaminated with iron from normal carbon steel, however, scratches on stainless steel do not detract from theircorrosion resistance in such application areas. This is due to the ‘self-healing’ nature of the passive surface layer on the steel.
Coloured finishes
Colours including blue, black, bronze, charcoal, gold, green and red are available on 316 and 304 stainless steel types. These colours can be applied to mill, patterned, polished, bead blasted or etched surface finishes and offers a wide range of colour and texture. The colour does not contain dyes or pigments, but relies on light interference path difference effects in a chemically thickened surface passive layer.
Generally colouring is done on tube sheet material before fabrication and so the scope for complex shapes or forms may be limited. Surface scratches are difficult to repair and so this range of finishes may not be suitable for high traffic areas and is better suited to cladding or roofing applications.
Patterned finishes
Cold rolled embossed, three-dimensional patterns to either one or both sides. These ‘2M’ finishes help mask scratches and marks and so are useful in high traffic areas, especially lift doors, fascias and lining panels. Tube Sheet with patterned rolled finishes, depending on the pattern depth, can exhibit improvements in stiffness for panel applications.
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