When tan rust spots appear on the surface of stainless steel products, people are surprised; they think that stainless steel does not rust and there might be some problem with the quality of the product. This lack of understanding of stainless-steel leads to a wrong view. Contrary to this, stainless steel rusts under certain conditions.
Stainless steel has the ability to resist not only atmospheric oxidation i.e. rust but also corrosion in acid, alkali or salt-containing medium. However, the corrosion resistance of the steel varies with its chemical composition, additive state, service conditions and the type of environmental medium it is used in. For example, the 304 steel tube has very excellent resistance to corrosion in a dry and clean atmosphere, but then moved to the coastal areas or in the sea fog containing a lot of salt, it rusts quickly. However, the 316 steel tube is resistant to seawater corrosion. Thus, the type of stainless steel that is resistant to corrosion and does not rust in specific conditions of the environment should be used.
Stainless steel has a surface of a very thin, strong, dense and stable chrome-rich oxidation film (protective film ) that prevents the continued infiltration of oxygen atoms to cause continual oxidation, and thus has the ability to resist corrosion. If for any reason, the film is destroyed, oxygen atoms in the air or liquid consistently seep in, resulting in continued separation of iron atoms and formation of loose iron oxides, making the metal surface rusted.
The surface film of stainless steel products is damaged in many forms, with the common situation in production and usage in daily life being as follows:
- Due to the heat of welding, the precipitation of carbide in the heat-affected zone near the welding seam is minimized, while the precipitation of carbide may lead to the intergranular corrosion (welding erosion) of stainless steel in some environments.
- The processes of stamping, stretching, cutting, grinding, drawing, etc. destroy the passivation film on the surface of stainless steel. Abrasions and scratches to stainless steel products also damage the protective film on the surface.
- Sometimes there is dust containing other metal elements on the surface of stainless steel or attachment of different metal particles. In humid air, the condensed water droplets between the attachment and stainless steel are connected in the form of a micro battery, which triggers an electrochemical reaction and damages the protective film, which is called electrochemical corrosion.
- Organic liquids (such as vegetable, noodle soup, sputum, etc.) adhere to the stainless steel surfaces and react in the presence of water and oxygen to produce organic acid corrosion on the metal surface persistently.
- Substances such as acids, alkalis, and salts (such as alkaline water of decoration walls, lime water sprays) cause local corrosion.
- Substances in the polluted air (such as the atmosphere containing a lot of sulfides, oxidized carbon and nitrogen oxide) react in the presence of condensed water leading to the formation of sulfuric acid, nitric acid, and acetic acid, etc. causing chemical corrosion.
The above conditions can cause damage to the protective film on the stainless steel surface and lead to corrosion. Therefore, to ensure that the metal surface is permanently bright and not corroded, we suggest:
- After the production and processing of stainless steel products, the passivation repair protective layer should be applied. This may include operations such as application of pickling passivate after removal of the welding spot to produce a new protective film, stainless steel passivate after repair stamping, stretching or other damages caused by the breach of the protective film layer.
- During use, the decorative stainless steel surface must be cleaned and scrubbed frequently to remove attachments, eliminating the external factors that cause modifications, and stopping the use of tools such as steel wire ball that easily damage the stainless steel surface.
- In coastal areas, 316 stainless steel should be used, which is resistant to seawater-corrosion.
- The chemical composition of some stainless steel tubes in the market does not meet the corresponding national standards, falling short of the material requirements of 304/316. This causes them to rust, which requires the users to carefully choose the products of reputable manufacturers.
Stainless steel handrails and stainless steel railings are very popular and are generally considered one of the best materials for balconies in coastal areas. They have been considered optimum for the last few years, perhaps decades. This is true up to a point, but there are significant shortcomings that the end-users and manufacturers will be disappointed if they don’t know or properly avoid.
Almost everyone who makes or manufactures stainless steel products finds them occasionally rusty or stained. This situation dissatisfies buyers since they pay for “stainless steel”. In some cases, it has been found that stainless-steel manufacturers point out that “stainless steel” means it has fewer stains; This may be a test of English, but it is a truer description.
Unity Metal Industry Limited is a stainless-steel railing tube and component-fitting manufacturer in Foshan, which specializes in the delivery of base covers, bar holders, elbows, end caps, glass clamps, handrail brackets, wall bracket, 25x21mm/ 42.4mm/48.3mm slotted tube fittings and LED handrails to the European, South American, and Australian Markets.
Unity Metal Industry Limited is a stainless steel handrail product company dedicated to the provision of high-quality handrail tube and fittings for clients.
Our company is located in Foshan, China, which has a long history of working in the stainless steel market. We boast a 2000 square meter plant, and the total annual output of different tubes and fittings reaches 8000 tons.
We commit to always deliver “THE HIGHEST QUALITY AT THE LOWEST PRICES”.
Unlike the old saying “Beauty doesn’t come cheap”, we provide high-standard handrail accessories at fsunitymetal.com. This is possible because of our being true manufacturers in China. Moreover, we ensure the provision of the lowest possible price rates to the customer without the involvement of any middleman.