Common Anti-Corrosion Technology Of Fasteners- Change The Structure Of The Steel

In the fastener industry, corrosion protection is an important subject that many people may be interested in. As a professional fastener manufacturer, Xinchi Fastener Company has rich industry experience, we are happy to introduce the fastener anti-corrosion technology to you. One of the anti-corrosion technologies of fasteners is to change the organizational form of steel. Specifically, it can be divided into two situations. One is to adapt the composition of steel, such as stainless steel screws; The second is to change the heat treatment state of steel. Next Xinchi Fastener Company will give you specific instructions.

A change in composition (eg stainless steel)

Stainless steel has excellent corrosion resistance and a good decorative effect, so it has a wide range of applications in various cities. It is generally believed that the corrosion resistance mechanism of stainless steel is mainly as follows.

1) When the content of Cr exceeds 13%, the electrode potential of steel will increase from negative to positive, making the steel matrix itself “inert”;

2) Cr will form a dense Cr-rich passivation film on the steel surface to further protect the matrix.

3) Stainless steel is divided into martensitic steel, ferritic steel, austenitic steel, and austenitic ferritic stainless steel, especially austenitic stainless steel with the best corrosion resistance, such as A2, A4 stainless steel.

Stainless steel mainly has the following deficiencies:

1) Yield strength is very low (generally not more than 300 MPa), so stainless steel is not suitable for the connection of major structural parts.

2) Stainless steel is easy to appear thread bite. When the stainless steel bolt is tightened, it is easy to cause damage to the surface of the thread. At this time, it will spontaneously produce a layer of oxidation, which aggravates the bolt sticking and locking.

3) Stainless steel is easy to produce intergranular corrosion. At a certain temperature, C and Cr in stainless steel will form compounds, especially near the grain boundaries, which will cause a “Cr-poor zone” at the grain boundaries, leading to grain boundary corrosion.

4) The poor corrosion resistance of CI medium (except A4 stainless steel).

5) The price is high (about 4 times that of Dacroc1).

Change of heat treatment state

Iron and steel materials are mainly polyphase structures (impurities, carbide, intermetallic compounds, and another second phase usually exists in steel as the cathode, and Fe matrix as the anode). There exists a potential difference between phase and phase in polyphase structure, forming corrosion microcells. The second phase may be the anode passivation phase or the cathode dissolution phase, both of which will affect the corrosion resistance of the matrix.

Stainless steel, for example, requires great care in welding and heat treatment. Stainless steel after high-temperature solution treatment, between 400C~850C heating, will produce a lot of CrsC, Cr, and C; Carbides precipitate along grain boundaries, forming Cr-poor regions near grain boundaries. The carbide is used as the cathode of the corrosion battery, and the Cr-poor region is used as the anode of the corrosion battery, which leads to the corrosion of the grain boundary, and its corrosion resistance will be greatly reduced.

Anji Xinchi Fasteners Co., Ltd. is a one-stop fastener and fastener solution company. As a reliable fastener supplier, we can offer types of fasteners, including  T-nuts, screws, washers, sleeves, bolts, rivets, and more. If you would like to know more about fasteners or have any fastener purchasing requirements, please do not hesitate to contact us and our experienced sales staff will get back to you as soon as possible.