How can degreasers avoid corrosion of metal surfaces?

How to avoid corrosion of metal surfaces by degreasing agents

Metal surface treatment is an important part of industrial production, and degreasing, as its first step, directly affects the quality of subsequent processes and the performance of the final product. However, while degreasing agents remove grease and dirt, they may also corrode the metal surface, causing material performance degradation and even safety hazards. Therefore, how to prevent degreasing agents from corroding metal surfaces has become an urgent problem to be solved.

1. Mechanism of degreasing agent corrosion on metal surface

The corrosion of degreasing agent on metal surface mainly comes from the following aspects:

Acidity and alkalinity: Strong acid or alkaline degreasing agents will destroy the oxide film on the metal surface, causing the metal substrate to be directly exposed to the corrosive environment and accelerating the corrosion process.

Oxidizing property: Some degreasing agents contain strong oxidizing substances, such as hydrogen peroxide, sodium hypochlorite, etc., which will oxidize the metal surface to form loose and porous corrosion products and reduce the corrosion resistance of the metal.

Electrochemical corrosion: The electrolyte in the degreaser promotes the formation of micro-batteries on the metal surface, accelerating the occurrence of electrochemical corrosion.

Stress Corrosion: Certain degreasers can react with areas of stress concentration on metal surfaces, causing stress corrosion cracking.

2. Measures to prevent degreasing agents from corroding metal surfaces

In order to avoid the corrosion of the metal surface by the degreasing agent, we can start from the following aspects:

1. Choose the right degreaser

Choose according to metal material: Different metal materials have different tolerance to degreasing agents. For example, active metals such as aluminum and magnesium should avoid using strong acid and alkaline degreasing agents, while steel can use alkaline degreasing agents.

Choose according to the type of dirt: Different dirt requires different degreasers. For example, grease dirt can use alkaline degreasers, while rust requires acidic degreasers.

Choose an environmentally friendly degreaser: Environmentally friendly degreasers usually use mild formulas, are less corrosive to metals, and are environmentally friendly.

2. Control degreasing process parameters

Control the degreasing temperature: Too high a temperature will accelerate the chemical reaction of the degreasing agent and increase the risk of corrosion to the metal.

Control the degreasing time: Too long degreasing time will cause excessive corrosion of the metal surface. The degreasing time should be reasonably controlled according to the actual situation.

Control the degreaser concentration: Too high a degreaser concentration will increase the risk of corrosion to the metal. The concentration should be adjusted reasonably according to the product instructions and actual conditions.

3. Strengthen metal surface pretreatment

Remove surface oxide scale: Oxide scale on the metal surface will hinder the penetration of degreasers and increase the risk of corrosion. The oxide scale should be removed by mechanical or chemical methods.

Cleaning surface oil stains: Oil stains on the metal surface will affect the penetration of the degreaser and should be pre-cleaned with a detergent or solvent.

4. Use corrosion inhibitors

Adding corrosion inhibitors: Adding corrosion inhibitors to the degreaser can effectively inhibit the corrosion of the metal surface. Commonly used corrosion inhibitors include organic amines, inorganic salts, etc.

Choose a degreaser containing corrosion inhibitors: Some degreasers contain corrosion inhibitors themselves, which can be more convenient to use.

5. Enhance post-processing

Timely cleaning: After degreasing, the metal surface should be rinsed with clean water in time to remove the residual degreasing agent.

Passivation treatment: For metals that are prone to corrosion, passivation treatment can be performed to form a dense oxide film on the metal surface to improve its corrosion resistance.

3. Case Analysis

Case 1: When cleaning aluminum alloy parts, an automobile manufacturer used a strong alkaline degreasing agent, which caused serious corrosion on the surface of the parts. After analysis, it was found that the strong alkaline degreasing agent destroyed the oxide film on the surface of the aluminum alloy, causing the base metal to be exposed to the corrosive environment. The solution was to use a weak alkaline degreasing agent and add a corrosion inhibitor, which effectively avoided the occurrence of corrosion problems.

Case 2: A steel plant used an acidic degreasing agent when cleaning steel plates, which caused rust on the surface of the steel plates. After analysis, it was found that the acidic degreasing agent reacted with the iron elements on the surface of the steel plates to generate rust. The solution was to use a neutral degreasing agent instead, strengthen post-treatment, and clean and dry the surface of the steel plates in time, effectively solving the rust problem.

6. Conclusion

The corrosion of metal surfaces by degreasing agents is a complex issue that requires comprehensive consideration from multiple aspects. By selecting appropriate degreasing agents, controlling degreasing process parameters, strengthening metal surface pretreatment, using corrosion inhibitors, and strengthening post-treatment, the corrosion of metal surfaces by degreasing agents can be effectively avoided and the quality and performance of metal products can be improved.