Common Anti-Corrosion Technology Of Fasteners-Membrane Treatment Technology

Fasteners are the most common parts in the mechanical equipment used for fastening connections. They are used in specific circumstances. The long-term interaction between fasteners and the environment will always change their state and performance, that is, corrosion, which is one of the main failure forms of fasteners. If the corrosion of fasteners is light, it will affect the detachability and repeated installation of threads, and if it is heavy, it will damage the strength of the connection between components, and even lead to the sudden failure of the workpiece, result in catastrophic accidents. Therefore, the corrosion protection of fasteners has been a topic of great concern.

As a professional fastener manufacturer, Xinchi Fastener Company can supply various high-quality fasteners, including 4-prong t nuts, bolts, screws, and so on. We are happy to introduce the common fastener anti-corrosion technology.

The anti-corrosion treatment of fasteners is generally through certain methods to form a covering layer or anti-corrosion layer on the workpiece surface to prevent the influence of the external environment on the fastener itself, and to achieve the effect of corrosion resistance. There are four main anti-corrosion technologies for fasteners: film treatment technology, metal coating technology, coating technology, and changing the internal structure of the metal (such as stainless steel).

In this article, we will mainly introduce membrane treatment technology.

Membrane treatment technology mainly refers to the process of generating a stable chemical (electrochemical) conversion film on the surface of a metal using chemical or electrochemical methods. For example, in the urban rail vehicle, the fastener film treatment is blackening or blueing and phosphating treatment.

Blackening or blueing

Blackening or blueing refers to the process of forming a layer of chemical oxide film on the surface of iron and steel parts (the main component is Fe, O,) after being treated at about 140 degrees in a concentrated alkaline solution containing oxidants.

Technical characteristics of blackening/bluing treatment:

1) Film thickness 0.5-1.5μm.

2) Neutral salt spray resistance test (NSS) is generally only 2 ~5 Hrs, at this time, the oxide film has been broken, and even a large number of rust will appear.

3) Low hydrogen embrittlement sensitivity, so it can be used as high-strength bolts.

4) As a fastener, the consistency of torque and preload is poor.

5) The color of blackening/bluing is brighter and the decorative effect is better.

6) Low cost.

Phosphating

Phosphating is a process in which iron and steel parts are immersed in a solution containing manganese, phosphoric acid, phosphate and other reagents to generate a phosphate conversion film that is insoluble in water on the surface of the metal.

Technical characteristics of phosphating treatment:

1) The film is firmly bound to the matrix (1 ~50 μm thick).

2)NSS can be up to 10~20 Hrs or even 72 Hrs.

3) Poor mechanical strength, and brittle quality.

4) As a fastener, its torque-preload consistency is very good.

5) The color is light gray and other dark colors, and the decorative effect is poor.

6) Hydrogen embrittlement sensitivity is low and can be used as high strength bolt.

7) Lower cost.

Anji Xinchi Fasteners Co., Ltd. is 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.