Chloride ions are very harmful to stainless steel. In the passivation process, the content of chloride ions in the passivation liquid should be strictly controlled, and the chemical materials used in passivation have limited requirements for chloride ions. The preparation of passivation liquid water and cleaning water also have strict water quality requirements for chloride ions to ensure that the passivation product is not attached to chloride ions to avoid future problems.

For stainless steel alloys, the lower the surface roughness, the smoother the surface, the more difficult it is for foreign bodies to attach, and the lower the probability of local corrosion. Therefore, stainless steel should be as finished as possible. In addition, the surface cleanliness of stainless steel is also very important, the final cleaning of the surface after passivation should be carefully carried out, because the residual acid promotes the cathode reaction, so that the film is broken, and the stainless steel is activated, and the corrosion resistance is greatly reduced.

Stainless steel passivated film belongs to thermodynamically inhibited metastable structure and its protective efficiency is related to the environmental medium. It should be cleaned regularly in use to remove harmful substances attached to the surface for a long time. Especially in the environment with chloride ions, avoid chloride ions in long-term milk attached to the surface and concentrated in water such as stainless steel for food utensils, time after contact with food, should be washed, to avoid ion action, and damage passivation film. Such as containers and equipment dairy products, the chloride ions contained in dairy products have a destructive effect on the passivation film, such as long-term dairy products, will lead to capacity and equipment corrosion perforation, so regular cleaning, so that the passivation film recovery.

The contents of martensite and chromium-nickel in stainless steel have a great influence on the passivation properties of stainless steel. Low nickel content leads to low clockwork performance. The passivation film performance of martensitic stainless steel is not as good as that of austenitic stainless steel. Therefore, in the daily use of stainless steel process, it is very important to pay attention to the use of stainless steel environment, according to the environment to choose the appropriate stainless steel varieties.

1. Surface Cleanliness
The surface of stainless steel is smooth, and it is difficult for foreign matter to adhere to it, so the probability of corrosion is extremely low. However, some stainless steel surfaces are relatively rough, and foreign matter can easily adhere to it, causing corrosion on the stainless steel surface. Therefore, this problem should be paid attention to during fine processing. In addition, the cleanliness of the stainless steel surface is also very important, and the final cleaning after passivation should be carried out carefully, because the residual acid promotes the cathode reaction, breaks the film layer, and activates the stainless steel, which greatly reduces the corrosion resistance.

2. Intrinsic Factors
Some components in some stainless steels will also affect the passivation film on their surface. For example, the martensite content and chromium-nickel content in a certain stainless steel strip have a relatively large impact on the passivation film. If the nickel content is relatively low, the passivation performance is much worse, and the passivation performance of martensitic stainless steel strips is also worse than that of austenitic stainless steel strips.

3. Chloride Ions
When storing stainless steel pipes, they must be kept away from environments such as ocean breezes, because the sea breeze and seawater contain a large amount of chloride ions, which are extremely harmful to stainless steel. During the passivation process, the chloride ion content in the passivation solution should be strictly controlled, and the passivation chemical materials used have limited requirements for chloride ions. The water used to prepare the passivation solution and the cleaning water also have strict water quality requirements for chloride ions to ensure that the passivation product does not adhere to chloride ions to avoid future troubles.

4. Use Environmental Media
The stainless steel passivation film belongs to a thermodynamically suppressed metastable structure. Its protective efficiency is related to the environmental medium. It should be cleaned regularly during use to remove harmful substances that have been attached to the surface for a long time. Especially in an environment with chloride ions, avoid long-term attachment of chloride ions to the surface and concentration in water. For example, stainless steel is used in food industry utensils. After each contact with food, it must be cleaned to avoid the action of chloride ions and damage to the passivation film.

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