Why does the metal surface still rust after anti-rust treatment?

Feedback from some metal parts manufacturers:

The product has taken anti-rust measures between processes, why do the parts still rust during transportation and storage? Some products also have rust spots before use? What is the reason?

The reasons for the rust of parts should be self-checked from the following points:

1. Anti-rust between processes

① Whether the anti-rust oil or anti-rust agent used for anti-rust of parts and semi-finished products between processes is regularly tested. Because the use of anti-rust oil and anti-rust agent is conditional, the effect strength is different in different environments and parts surfaces, and not all parts of all sizes can be operated in the same way.

② Before anti-rusting the product surface, whether the metal surface has been cleaned (cleaning the dirt and other chemical factors contaminated in the previous processes, etc.).

If the metal parts are not cleaned according to the process requirements before applying the anti-rust oil, and there are residual sweat, moisture, dust and other corrosive media on the surface, it will indirectly contaminate the anti-rust oil and anti-rust agent, and the anti-rust layer will wrap the dirt inside, causing the metal surface to rust under the action of pollutants for a long time.

③ Whether it is cleaning or rust prevention of parts, whether the staff strictly wear relatively clean gloves. If it is not carried out according to regulations, hand sweat will also contaminate the surface of parts and is also one of the factors causing rust.

④ Cleaning and rust prevention is a continuous operation. After cleaning the metal surface, rinsing, drying (drying), and cooling, the surface rust prevention operation should be carried out in time to avoid the metal surface being exposed to the air for a long time.

2. Rust prevention of finished products

① For the rust prevention of metal parts, the finished products will be soaked in anti-rust oil or anti-rust agent in the end. If the anti-rust process or treatment method is improper, the expected anti-rust effect cannot be achieved, and even the risk of rust will increase.

For example, when hot-dip oil is applied, the temperature is too high, so that the oil does not form a complete and uniform protective film on the metal surface; or after the parts are hot-dip oiled, they are packaged without cooling.

② The use of unqualified packaging materials, poor packaging quality, and packaging damage will cause corrosive media to invade the metal and rust.

Some packaging materials will rub against the anti-rust layer on the metal surface, thereby destroying the anti-rust layer. What's worse, the anti-rust packaging materials used are incompatible with the anti-rust oil and anti-rust agent on the surface.

It is best to choose anti-rust packaging with good stability and long anti-rust cycle, and there is no need for multi-layer packaging.

In short, if there is still rust after anti-rust, it means that the existing anti-rust method is insufficient, or the anti-rust product used does not meet the actual anti-rust requirements, then it is necessary to change the anti-rust plan and technology in time to avoid economic losses.