Why does stainless steel rust ?

Why does stainless steel rust ?

When brown rust spots (spots) form on the surface of stainless steel pipes. people are  amazed and believe that "stainless steel is never rusty, and if it gets rusty, it is not stainless steel" It is possible that there are some problem of the stainless steel's quality. In actuality, this is a partial misperception regarding the insufficient knowledge about stainless steel. In some situations, stainless steel can also rust. stainless steel has the ability of stainless. and also have the ability of corrosion resistance at the same time. However, the stainless steel's chemical makeup, the state of mixing, the usage circumstances, and the type of environmental media all affect how resistant it is to corrosion. Similar to 304 stainless steel pipes, in a dry environment, they are absolutely impervious to tarnishing. However, once they are transported to the Riviera, where there is a high concentration of salts in the sea fog, they quickly rust. The 316 stainless steel pipe worked effectively as well. As a result, no type of stainless steel can withstand rust and corrosion in any environment.

The stainless steel surface film can be damaged for a variety of causes. The typical ones encountered every day are as follows:

In order to prevent oxygen atoms from continuing to enter and oxidize, stainless steel relies on a layer of extremely thin, solid, dense, and stable chromium-rich oxide film (protective film) to form on its surface. Once for whatever cause, the film is continually harmed, oxygen atoms in the air or liquid continuously enter, iron atoms continuously split out to create loose iron oxide, and the metal surface is continuously corroded. The stainless steel surface film can be damaged for a variety of causes. The common ones in daily life are as follows:

1. On the surface of stainless steel, dust with other metal components or attachments of heterogeneous metal particles accumulate. Condensed water between the attachments and stainless steel forms a microbattery while in humid air, which starts an electrochemical reaction and safeguards the device. Electrochemical corrosion, which is the cause of the membrane deterioration, is present.

2. Organic juices that stick to the surface of stainless steel include vegetable, noodle, sputum, and other juices. Organic acids are created when oxygen and water are present, and over time, these organic acids will corrode the metal surface.

3. Local corrosion results from the surface of stainless steel adhering to acid, alkali, and salt substances (such as lime water splash and alkali water wall painting).

4. When it comes into contact with condensed water in contaminated air (such as an environment that contains significant amounts of sulfide, carbon oxide, and nitrogen oxide), it will produce liquid points of sulfuric acid, nitric acid, and acetic acid, which will lead to chemical corrosion.

We advise the following to keep the metal surface corrosion-free and permanently bright:

The protective coating on the stainless steel surface may be damaged and corroded by the aforementioned circumstances. Consequently, to guarantee that the metal surface is consistently brilliant and uncorroded, we advise:

1. In order to remove attachments and get rid of outside influences that lead to rust and corrosion, the surface of decorative stainless steel needs to be cleaned and scrubbed periodically.

2. Stainless steel made of material 316 should be used in coastal areas since it can withstand corrosion from seawater.

3. Some stainless steel pipes on the market do not conform to the applicable national norms or the specifications for 304 materials due to their chemical make-up. As a result, it will also lead to rust, thus consumers must carefully select goods from reliable vendors.

Is stainless steel magnetic as well?

Stainless steel is frequently tested for authenticity and quality using magnets. It is seen as good and real if it doesn't attract or have magnetism; if it does, it is regarded as a fake. In actuality, this is a very biased, unworkable, and incorrect method of differentiation.

There are numerous varieties of stainless steel, which can be categorized into a number of groups based on the hierarchical structure at room temperature:

1. Austenitic type: such as 201, 202, 301, 304, 316, etc.;

2. Martensite or ferrite type: such as 430, 420, 410, etc.;

Martensite or ferrite is magnetic, but austenite is either non-magnetic or rather faintly magnetic. The majority of stainless steel used for decorative tube sheets is austenitic 304 material, which is typically non-magnetic or weakly magnetic but can also appear magnetic due to changes in chemical composition or unique processing conditions brought on by melting. Why can't this be regarded as counterfeit or unqualified? As was already mentioned, martensite or ferrite is magnetic, but austenite is either non-magnetic or rather faintly magnetic. Austenitic 304 stainless steel will occasionally generate a tiny quantity of martensite or ferrite as a result of composition segregation or incorrect heat treatment during smelting. bodily tissues. This will result in 304 stainless steel having little magnetic. Additionally, the microstructure of 304 stainless steel will change to martensite following cold working. The amount of martensite transformation and magnetic properties of the steel increase with the amount of cold working deformation. Without any discernible magnetic induction, 76 tubes are created, similar to a batch of steel strips, and 9.5 tubes are produced. The larger bending distortion makes the magnetic induction more noticeable. In particular, the corner portion, the deformation is more extreme and the magnetism is more visible in the square, rectangular pipe than it is in the circular pipe. By restoring the stable austenite structure through high temperature solution treatment, the magnetism of 304 steel induced by the aforementioned factors can be fully eliminated. Because of the aforementioned factors, the magnetism of 304 stainless steel consistently exhibits weak magnetism and is therefore lower than that of other stainless steels, such as 430 and carbon steel. This teaches us that stainless steel should be designated as 304 or 316 material if it exhibits weak magnetic or no magnetism at all; if it e