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Resistance to corrosion of stainless steel results from the existence of a passive layer of chromium oxide which is renewed
spontaneously when in contact with the air. Any phenomenon interfering with the creation of this layer is likely to cause cor-
rosion.
This is why stainless steel surfaces must be regularly rid of miscellaneous contamination which may damage the level of re-
sistance of the passive layer, and also ensure the maintenance steps are observed. (Preparation to cleaning / cleaning / rinsing
/ disinfection / rinsing / drying).
Regular maintenance with extended rinsing with water is the best method to renew and maintain the passive layer.
Each of the steps linked with maintenance presents risks of damaging the passive layer: using hard water / overdosing deter-
gents / using chlorine-based detergents / food residue on the products / insufficient rinsing.....
Whenever corrosion appears, the element or step having led to it must be identified.
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Advice
:
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maintain stainless steel surfaces clean and dry. Ensure there is a sufficient flow of air.
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clean daily to remove scale, grease and any food residue. Corrosion can form under these layers by lack of air inlet.
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daily cleaning can be performed with a damp cloth. If necessary :
* use soapy water, cleaning products with low chloride content, javel-free detergents, window degreasers.
* remove hard stains with a non metallic brush (plastic material, natural bristles or stainless steel wool).
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do not scratch the surfaces with metals other than stainless steel, and more particularly, never use iron brushes.
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remove fresh rust stains with soft abrasive agents or fine emery cloth.
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for larger stains, use hot oxalic acid with a 2-3% concentration. If necessary, apply a treatment with nitric acid concentra-
ted at 10%.
After treatment, wash thoroughly with water and wipe.
The use of acid is reserved to skilled persons and complying with regulations.
Product to ban
:
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Javel water and chlorine based products
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hydrochloric acid
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iron oxide abrasive powders.
If washing is carried out in a tunnel, do not air dry at a temperature higher than 70°C.
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