Stainless
steel is selected for applications where their
inherent corrosion
resistance, strength and
aesthetic appeal are required. However, dependent on the service conditions,
stainless steel will stain and discolour due to surface deposits and so cannot
be assumed to be completely maintenance-free. In order to achieve
maximum corrosion
resistance and aesthetic
appeal, the surface of the stainless
steel must be kept clean. Provided the grade of stainless steel and
the surface
finish are correctly
selected, and cleaning schedules carried out on a
regular basis, good performance and long service life will result.
Factors affecting
maintenance
Surface contamination and the formation
of deposits on the surface of the stainless
steel must be prevented.
These deposits may be minute particles of iron or rust generated during
construction. Industrial and even naturally occurring atmospheric conditions can
produce deposits which can be equally corrosive, e.g. salt deposits from marine
conditions.
Working environments
can also provide aggressive conditions such as heat and humidity in swimming
pool buildings. These
conditions can result in surface discolouration of stainless steel and so
maintenance on a more frequent basis may be required.
Modern processes use
many cleaners, sterilizers and bleaches for hygienic purposes. Proprietary
solutions, when used in accordance with makers’ instructions, should be safe but
if used incorrectly (e.g. warm or concentrated), may cause discolouration
or corrosion on stainless steel.
Strong acid solutions are sometimes used to clean masonry and tiling of
buildings. These acids should never be used where contact with metals, including
stainless steel, is possible. If this happens, the acid solution must be removed
immediately, followed by dilution and rinsing with cleaning water.
Maintenance programme
With care taken
during fabrication and installation, cleaning before ‘hand-over’ should not
present any problems. More attention may be required if the installation period
has been prolonged or hand-over delayed. Where surface contamination is
suspected, immediate cleaning after site fixing should avoid problems later.
Food handling, pharmaceutical, aerospace and certain nuclear applications may
require extremely high levels of cleanliness applicable to each industry.
The frequency
of cleaning is dependent on the
application – a simple rule is:
Clean the metal when
it is dirty in order to restore its original appearance.
This may vary from
once to four times a year for external applications, but may be daily for items
in ‘hygienic’ applications. Recommendations on cleaning frequencies in
architectural applications are shown below.
Cleaning frequency
in architectural applications
| Location | 430 (1.4016) | 304 (1.4301) | 316 (1.4401) |
| Internal | As required to maintain appearance or design | ||
| Suburban or rural | 6-12 month intervals (as appropriate to location and design) | ||
| Industrial or urban | Stainless Steel Grade not recommended | 3-6 months | 6-12 months |
| Coastal or marine | Stainless Steel Grade not recommended | Grade not recommended | 6-12 months |
Source: Zhejiang
wilsonpipeline Pipe Industry Co., Limited (www.wilsonpipeline.com)
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