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Cleaning Care Maintenance of Stainless Steel
The attractive and hygienic surface appearance of stainless steel products cannot be regarded as completely maintenance free.
All stainless steel grades and finishes of may in fact stain, discolour or attain an adhering layer of grime in normal service.
To achieve maximum corrosion resistance the surface of the stainless steel must be kept clean.
Provided the grade, condition and surface finish were correctly selected for the particular service environment, fabrication and installation procedures were correct and that cleaning schedules are carried out regularly, good performance and long life will be achieved.
Frequency and cost of cleaning of stainless steel is lower than for many other materials and this will often out-weigh higher acquisition costs.
principles apply whether the item concerned is a simple kitchen utensil or a
large and complex architectural installation.
Industrial, commercial and even domestic and naturally occurring atmospheric conditions can result in deposits which can be quite corrosive. An example is salt deposits from marine conditions. Working environments can also create more aggressive conditions, such as the warm, high humidity atmosphere above indoor swimming pools.
This particular environment has in a small number of instances been found to be highly aggressive, and specialist advice should be obtained. Aggressive operating environments can increase the speed of corrosion and therefore require more frequent maintenance.
Modern processes use many cleaners, sterilisers and bleaches for hygienic purposes.
These proprietary solutions, if appropriate for use with stainless
steel and when used in accordance with their makers' instructions are safe, but
if used incorrectly (e.g. warm or concentrated) can cause discolouration and
corrosion on the surface of stainless steels.
Strong acid solutions (e.g. hydrochloric acid or “spirits of salts”) are sometimes used to clean masonry and tiling during building construction but they should never be permitted to come into contact with metals, including stainless steel.
should happen the acid solution must be removed immediately by copious water
flushing, but even if promptly removed the appearance of the steel may be
A rule of thumb for many exterior building installations is to clean the stainless steel whenever the nearby glass needs cleaning. This may vary from once to four times a year for external applications or it may be once a day for an item in hygienic or aggressive situations. In many applications the cleaning frequency is after each use. Suggested cleaning intervals are as in this table – these should be modified by experience.
Note that natural rain is an effective cleaner – those items that are not washed by rain water may need more frequent maintenance cleaning.
• Steel storage racks
• Handling Equipment
• Grinding wheels, wire brushes, finishing belts
• Contamination by grinding or welding sparks from adjacent carbon steel
• Grades with at least 16% chromium (except free machining grade such as 303):
20-50% nitric acid, at room temperature to 40oC for 30-60 minutes.
• Grades with less than 16% chromium (except free machining grades such as 416):
20-50% nitric acid, at room temperature to 40oC for 60 minutes.
• Free machining grades such as 303, 416 and 430F: 20-50% nitric acid + 2-6%
sodium dichromate, at room temperature to 50oC for 25 40 minutes
• Grades with at least 16% chromium (except free machining grades): 15-25%
nitric acid + 1-8% hydrofluoric acid, at 20 to 60oC for 5-30 minutes.
• Free machining grades and grades with less than 16% chromium such as 303, 410
and 416: 10-15% nitric acid + 0.5-1.5% hydrofluoric acid, at 20 to 60oC for 5-30
An enhanced appearance will be achieved if the cleaned surface is finally wiped dry. Specific methods of cleaning are as in the table on the next page.
These are recommendations only, and it must be recognised that there are risks associated with all cleaning operations. All such treatments must be evaluated by the user.
All residues must be flushed to a treated waste stream (refer to local water authorities for regulations and assistance). Always dilute by adding acid to water, not water to acid. Use acid-resistant containers, such as glass or plastics.
If no dulling of
the surface can be tolerated a trial treatment should be carried out; especially
for pickling operations. All treatments must be followed by thorough rinsing.
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