Application of Chemical Auxiliaries in Metal Processing

Metal processing includes metal cleaning, surface coating and metal turning, milling, planing, cobalt, rolling, casting and other processing processes. In order to improve product quality, reduce cost and save energy, some auxiliaries are often used in the processing process, among which non-ionic surfactants play a very important role.

Introduction to nonionic surfactants

Nonionic surfactants are surfactants that do not produce ions in aqueous solutions. The solubility of non-ionic surfactants in water is due to the strong hydrophilic functional group in the molecule, which is an important variety used in large quantities. With the development of the petroleum industry, its output will continue to increase. Non-ionic surfactants have the properties of wetting, foaming, solubilizing and defoaming.

Second, the application of non-ionic surfactants in metal processing

1, the application of metal cleaning

Metal cleaning runs through the entire metal processing process. Non-ionic surfactants play a role in chemical cleaning, such as washing, emulsification, penetration, adsorption, dissolution and so on, and have played an increasing role in pickling, alkali washing, corrosion inhibition, oil removal and other cleaning processes. At present, water-based cleaning with non-ionic surfactants as the main body has become the main development direction of metal cleaning.

Advantages of water-based metal cleaning agent: strong cleaning power, high cleaning efficiency; There is no damage to the metal itself during the washing process, and no corrosion to the metal after washing; Good safety performance, does not pollute the environment; Energy saving, low washing cost.

The water-based cleaning agent is generally composed of non-ionic surfactants and anionic surfactants, and several auxiliary agents are added. The cleaning mechanism is: with the emulsification, wetting, penetration, solubility, dispersion and other effects of non-ionic surfactants, the adhesion of oil on the metal surface is weakened, and then mechanical stirring, washing, heating, ultrasonic and other physical methods are applied to make the oil out of the metal surface.

The surfactants commonly used in metal cleaning are: fatty alcohol polyepoxy ethane ether, alkyl phenol polyepoxy ethane ether, sodium dodecyl benzene sulfonate, dodecyl glycol amide, sodium methoxyfatty amide benzene sulfonate, etc.

2, the application of metal phosphating

Phosphating is the treatment of metals with a dilute solution containing phosphoric acid, phosphates and other chemicals. The metal surface reacts chemically with phosphoric acid and phosphate medium in the above solution and transforms into a complete insoluble metal phosphate layer with medium corrosion protection. This phosphate conversion film on the metal has a variety of uses, it can improve the paint and metal bonding and corrosion resistance; It can also be used as a carrier for anti-rust oil, a carrier for lubricants in metal cold working and a lubricant for friction tables.

The role of non-ionic surfactants in metal phosphating treatment: the oil on the surface of the metal has the emulsification and solubilization effect to prevent the dirt from resettling; Make the solution wet and permeate, which is conducive to the contact between the phosphating solution and the metal surface; Reducing the surface tension of the liquid is conducive to the escape of hydrogen in the phosphating reaction, strengthening the polarization of the cathode, and thus accelerating the phosphating film formation process.

3, the application of metal plating

The role of non-ionic surfactants in metal plating: leveling, brightening, diffusion, changing the physical properties of the coating, inhibiting the escape of acid mist, etc. It can improve the performance of electrolyte and improve the quality of coating.

The commonly used surfactants in metal plating are: Pinga, OP emulsifier, sodium dodecyl sulfate, fatty acid polyethylene oxide ester, polyethylene oxide castor oil, etc.