Stainless steels are resistant to corrosion thanks to a thin layer of oxides chromium on their surface, which forms spontaneously in the presence of oxygen or through chemical passivation. To ensure maximum protection against corrosion, the stainless steel surface must be clean and have access to oxygen, which, by combining with chromium, creates a protective layer of chromium oxides — the passive layer.
It is common to believe that stainless steel is resistant to all forms of corrosion and does not require maintenance. This misconception often stems from the name of this group of steels – “stainless” – and a misinterpretation of that term. In English stainless steels are called “Stainless steels” – Stain-less, which means less prone to corrosion, intended to warn about the possibility of corrosion. Unfamiliar people who previously used non-alloy, low-alloy steels (black steels) often assume that stainless steels do not require additional maintenance, taking the name “stainless” as a guarantee of no corrosion. In reality, to maintain corrosion resistance, stainless steel requires regular maintenance, mainly cleaning. Its resistance depends on a thin passive layer on the surface, and any contaminants, deposits or foreign particles can damage it. This is particularly important in environments containing chloride salts, sulfides or other metal substances prone to corrosion. In such conditions the surface of stainless steel may become discolored, be covered with corrosion products and begin to corrode.
Stainless steel requires regular maintenance and cleaning, which should be included in the product warranty conditions, indicating to the user the appropriate cleaning methods, frequency and agents to use and avoid (e.g. do not use steel brushes, products containing harsh abrasives, chlorides, fluorides, bromides, iodides, acids, bleaches). These actions aim to maintain operating conditions so that stainless steel does not corrode.
Below you will find some tips for cleaning and maintaining stainless steel and important aspects to pay attention to.
To clean industrial concrete floors, avoid contact with detergents intended for cleaning concrete (containing chlorides) and protect the surface from contact or rinse thoroughly with clean water.
When cleaning steel it may be necessary to use harmful chemicals. Follow the product safety recommendations (health hazard) and the instructions for their use (possibility of corrosion). Do not exceed the allowable contact time of the medium with the stainless steel, and after use always thoroughly rinse with clean water.
Avoid cleaning surfaces directly in the sun or at excessively high temperatures.
When cleaning stainless steel:
– Avoid cleaning with inorganic acids (especially hydrochloric acid or bleaches), which can cause discoloration and pitting corrosion.
– Never use materials that are strongly abrasive or steel wool.
– Do not allow stainless steel to come into contact with non-alloy steel, because particles of that steel will undergo accelerated corrosion on the surface of the stainless steel.
In the case of routine cleaning:
– Remove solid dirt and contaminants by rinsing with clean water and wiping the surface with a soft cloth.
– For heavier contamination, use a mild soap or detergent (e.g. ammonia, baking soda, vinegar, citric acid) and a soft nylon brush.
– After cleaning rinse thoroughly.
– When cleaning components, it is recommended to perform this at least once a year (more often in marine and industrial environments).
To remove contamination originating from non-alloy steel and iron particles, you can use a solution of oxalic acid applied to the surface with a soft cloth. Leave on the surface for a few minutes (do not rub) to dissolve the contaminants, and then rinse thoroughly with water.
In the case of light rust use household cleaners intended for stainless steel containing calcium carbonate or citric acid, and then rinse thoroughly with water.
In the case of moderate staining use products based on phosphoric acid or a 10% solution of phosphoric acid. Spray the surface and leave for 30–60 minutes (or according to the manufacturer’s recommendation). After cleaning neutralize the acid with diluted ammonia or a mild alkaline detergent, and then rinse thoroughly with water.
In the case of heavy rust seek professional services or dedicated products for pickling and passivating steel. After treatment always rinse the surface thoroughly with water.
Stainless steel is a material with high corrosion resistance, but it requires proper maintenance to retain its properties for many years. Regular cleaning and care of the surface are the key to ensuring the durability and aesthetics of stainless steel products.
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