Classification of non-phosphorus degreasing agent, how to choose degreasing agent?

According to the composition of degreasing agents, degreasing agents can be divided into three categories: first, organic degreasing agents, such as kerosene, gasoline, trichloroethylene, carbon tetrachloride and other degreasing agents. These degreasing agents are only crude degreasing agents, and cannot be directly plated after degreasing. The second type is water-based degreasing agent, which is composed of inorganic base, salt and surfactant. This kind of degreasing agent is the main body of electroplating degreasing agent. The third type is the mixed degreasing agent of inorganic and organic substances, also known as emulsion degreasing. It is mainly based on surfactant, adding kerosene or gasoline and water to form lotion, which is rarely used in production. In the process of electroplating, water-based degreasing agent is mostly used. It is composed of alkali metal hydroxide, carbonate, phosphate, silicate and surfactant. It is mainly used for chemical degrease, but also a small amount for electrolytic degrease and ultrasonic degrease.

According to the different principles of chemical degreasing, this degreasing agent is divided into three categories.

The first type is saponification degreasing. The oil stain on the metal surface and the alkaline substance in the degreasing agent undergo saponification reaction, which turns the oil into a water-soluble fatty acid salt to achieve the purpose of degreasing. This kind of degreasing agent has certain selectivity for oil. For example, animal oil and vegetable oil can undergo saponification reaction. But for mineral oil, this degreaser can do nothing. This requires the second type of degrease-emulsifying degreaser.

Adding surfactant with the function of emulsifying oil into the first type of degreasing agent becomes the second type of emulsifying degreasing agent. Under the synergistic action of inorganic salts and alkalis (such as sodium carbonate and sodium hydroxide), surfactants emulsify oil and disperse it into water to remove oil on metal surface.

The third type of degreaser is displacement degreaser. Its composition is similar to the second type of emulsified degreasing agent. The difference lies in the difference of surfactants. This kind of degreasing agent has strong penetration ability. It first relies on the surface active molecules to penetrate into the oil and metal surfaces and separate them. Under the action of gravity, the grease will float away from the metal interface.

The degreasing principles of the three types of degreasing agents are different, but the degreasing results are the same. From an economic point of view, the disadvantages of saponification degreasing are that it requires a high temperature and a large waste of energy. Generally, it needs to be above 70 ℃ to degrease, and the effect on mineral oil is very poor. Emulsion degreasing has little restriction on oil and can be used at a lower temperature, generally 50~70 ℃. The replacement degreasing can be used at a lower temperature, generally at 10~50 ℃. However, the replacement degreaser has a poor effect on wax removal, and cannot remove paraffin, vaseline, polishing paste and other grease at normal temperature. However, displacement degreaser is still effective for most mineral oils. For example, 988 low-temperature metal degreasing powder of Beijing Simplex Company belongs to this type of degreasing agent. Its major advantage is not only fast degreasing, but also energy saving.

Although we have introduced the performance and degreasing principle of the above three types of degreasing agents, they are not isolated, but related to each other. For example, adding sodium hydroxide, sodium carbonate, sodium phosphate (or sodium silicate) into the water will make a saponified degreasing agent. When the degreaser temperature rises to above 70 ℃, the oil will saponify with the degreaser. Add surfactant, such as OP-10, to the degreaser, and the temperature will reach 50~70 ℃. Then the oil will be removed after emulsification by the emulsifier, and the degreaser will become emulsified degreaser (type II degreaser). By adding some surfactants to the degreaser, it can become a displacement degreaser, which can be used between 10 and 50 ℃.

We should know the type of degrease before selecting degreaser. If it is waxy grease, such as polishing paste, stretching oil, vaseline, etc., emulsified degreasing agent should be preferred. At this time, if the high temperature above 70 ℃ is used, combined with ultrasound, the effect will be better. If it is a common grease, it is better to choose displacement degreaser, which can degrease at room temperature and save energy significantly.

If there is a lot of dust on the surface of parts, electrolytic degrease shall be supplemented after chemical degrease, or scrubbing degrease shall be used.

A displacement degreaser can also be selected to remove different oils at different temperatures. However, this method needs to use a lower concentration at high temperature, otherwise it will be more difficult to remove the surfactant material from the parts.

When using degreasing agent, not only its performance but also economic factors should be considered. The service life of degreasing agent is the main factor that determines the cost. The order of life of degreasing agent from long to short is: displacement type>emulsification type>saponification type.