Why does the surface of metal parts still rust after rust prevention? What are the reasons for this?

Feedback from certain metal parts manufacturers:

The product has already taken rust prevention measures in the process, 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 rust on the parts should be self checked from the following points: 

1、 Rust prevention between processes 

①Is the rust prevention oil or rust inhibitor used for parts and semi-finished products regularly tested during the process. Because the use of anti rust oil and anti rust agent is conditional, the strength of action varies in different environments and parts surfaces, and not all sizes of parts can be operated using the same method. 

② Before rust prevention is applied to the surface of the product, is it ensured that the metal surface has been cleaned thoroughly (dirt and other chemical factors contaminated in the previous steps of cleaning). 

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

③ Whether it is cleaning or rust prevention of parts, do workers strictly wear relatively clean gloves. If not carried out according to regulations, hand sweat can also contaminate the surface of the parts and is one of the factors that can cause rust. 

④leaning and rust prevention is a continuous operation. After cleaning the metal surface, it should be rinsed, dried (air dried), and cooled. The surface rust prevention operation should be carried out in a timely manner to avoid long-term exposure of the metal surface to the air. 

2、 Rust prevention of finished products 

① The rust prevention of finished metal parts will be carried out by soaking in rust preventive oil or rust inhibitor in the final stage. If the rust prevention process or treatment method used is inappropriate, the expected rust prevention effect cannot be achieved, and even the risk of rusting will be increased. 

For example, when applying hot dip oil, the temperature is too high, resulting in the oil not forming a complete and uniform protective film on the metal surface; Or packaging can be carried out without cooling after the parts are hot dipped in oil. 

② Unqualified packaging materials, poor packaging quality, and damaged packaging can all cause corrosive media to invade metal and rust. 

Some packaging materials may rub against the rust prevention layer on the metal surface, thereby damaging the rust prevention layer. Moreover, the rust prevention packaging materials used are incompatible with the rust prevention oil and rust inhibitor 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 summary, if there is still a problem of rusting after rust prevention, it is due to a lack of existing rust prevention methods, or if the rust prevention products used do not meet the actual rust prevention requirements, it is necessary to promptly change the rust prevention plan and technology to avoid causing economic losses.