All grades of stainless steel will stain and discolour due to surface deposits and can not be considered completely maintenance-free. In order to retain maximum corrosion resistance and aesthetic appeal, the surface of 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 then good performance and long service life are assured.
Factors Affecting Maintenance
- Surface contamination and the formation of deposits must be prevented. These deposits may be minute particles of iron or rust from other sources used in the building of new premises and not removed until after the stainless steel items have been fixed. Industrial and even naturally occurring atmospheric conditions can cause deposits that can be equally corrosive, e.g. salt deposits from marine conditions.
- A working environment which offers more aggressive conditions, e.g. hot & humid, such as in a swimming pool, increases the speed of discolouration and therefore requires maintenance on a more frequent basis. Modern processes use many cleaners, sterilisers and bleaches for hygienic purposes. All these proprietary solutions, when used in accordance with makers’ instructions, are safe, but if used incorrectly (e.g. warm or concentrated), can cause discolouration and corrosion on the surface of any quality of stainless steel.
- Strong acid solutions are sometimes used to clean masonry and tiling of buildings but they should never be permitted to come into contact with metals, including stainless steel. If this should happen, the acid solution must be removed immediately by copious applications of water.
- The selection of the correct surface finish on stainless steel makes its cleaning and maintenance much easier. A dry ground finish leaves many microscopic tears in the surface, allowing a build-up of dirt. A clean wet-cut finish has few surface tears, preventing dirt build-up and making cleaning easier.
General Cleaning Methods
Stainless steel is easy to clean. Washing with soap or a mild detergent and warm water, followed by a clear water rinse, is usually quite adequate for domestic and architectural equipment. An enhanced aesthetic appearance will be achieved if the cleaned surface is wiped dry.
Where stainless steel has become extremely dirty with signs of surface discolouration, (perhaps following a period of neglect or misuse), methods of cleaning are detailed in the chart.
Maintaining Stainless Steel
Provided care is taken during fabrication and installation, final cleaning before handing over to the client should present no special problems, although more attention than normal may be required if the installation period has been prolonged. Where surface contamination is suspected, immediate attention to cleaning after on-site fixing will encourage a trouble- free product life. Food handling, pharmaceutical, aerospace and certain nuclear applications require extremely high levels of cleanliness.
Advice is often sought concerning the frequency of cleaning stainless steel and the answer is quite simple: “Clean the metal when it is dirty in order to restore its original appearance”. This may vary from one to four times a year for external applications or it may be once a day for items in hygienic or aggressive situations. Frequency and cost of cleaning is lower with stainless steel than with any other materials and will often outweigh the initial higher cost of this superior product.
Specialist Cleaning
Buildings
Careful planning is necessary to achieve and maintain the desired surface appearance on external parts of the buildings. The choice of cleaning process is influenced mainly by the contaminant to be removed, the required degree of cleanliness and the cost of the operation. The smooth surface of stainless steel does not encourage dirt deposits and there is little danger of superficial corrosion roughening the metal surface.
External
Rain plays an important part in the washing-down of a building. Sheltered areas will collect dirt which, if not washed away periodically, could lead to deterioration of appearance or corrosion. In highly industrialised or coastal areas more frequent cleaning may be required than in rural areas or where clean air regulations apply. To remove normal atmospheric dirt, sponging down with water containing soap, detergent or ammonia, followed by rinsing with clear water and wiping dry, is generally sufficient.
Domestic, Institutional and Catering Equipment
In general, cleaning is carried out to restore the original surface appearance, prevent corrosion and maintain hygienic conditions. Stainless steel is easy to clean and washing with soap or a mild detergent and warm water, followed by a clear water rinse, is usually quite adequate for domestic, architectural and commercial catering equipment. If the water is hard, the steel should then be dried with a soft cloth to prevent water spotting.
Buildings
Careful planning is necessary to achieve and maintain the desired surface appearance on external parts of the buildings. The choice of cleaning process is influenced mainly by the contaminant to be removed, the required degree of cleanliness and the cost of the operation. The smooth surface of stainless steel does not encourage dirt deposits and there is little danger of superficial corrosion roughening the metal surface.
External
Rain plays an important part in the washing-down of a building. Sheltered areas will collect dirt which, if not washed away periodically, could lead to deterioration of appearance or corrosion. In highly industrialised or coastal areas more frequent cleaning may be required than in rural areas or where clean air regulations apply. To remove normal atmospheric dirt, sponging down with water containing soap, detergent or ammonia, followed by rinsing with clear water and wiping dry, is generally sufficient.
Domestic, Institutional and Catering Equipment
In general, cleaning is carried out to restore the original surface appearance, prevent corrosion and maintain hygienic conditions. Stainless steel is easy to clean and washing with soap or a mild detergent and warm water, followed by a clear water rinse, is usually quite adequate for domestic, architectural and commercial catering equipment. If the water is hard, the steel should then be dried with a soft cloth to prevent water spotting.
Notes for designers
Today more and more designers, fabricators and end- users are realising that the total cost of equipment over the required period of service can be more important than initial cost. Charges for maintenance, repair and replacement of inferior quality materials within that life period will often outweigh a higher initial capital cost associated with more durable materials. It is, thus important to select the correct finish at the outset.
Stainless steels offer long life and require far less cleaning and maintenance than most constructional methods. Provided the grade of stainless steel appropriate for the service environment is selected, it has been polished correctly and cleaning schedules are carried out on a regular basis, good performance and long service life are assured. Surface finish also plays an important role, not only for appearance but also for ease of maintenance.
