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Surfactants are widely used in the entire process of electroplating technology.

The following is a brief description of some functions:

1. Application in alkaline degreasing

Before electroplating, the metal workpiece must first be degreasing and cleaning to make its surface clean. Otherwise, the deposition layer will be poorly bonded on the surface, and in severe cases, the deposition layer may not even be obtained. Typical formula of degreasing liquid for carbon steel parts: sodium hydroxide 20～309/L, trisodium phosphate 30～409/L, sodium carbonate 30～409/L, OP emulsifier 1～29/L, 30～50. C. The oil stains on the surface of the workpiece include animal and vegetable oils and mineral oils. Animal and vegetable oils and fats can undergo a saponification reaction in an alkaline solution to form water-soluble soap and glycerin for removal; while mineral oil or other non-saponifiable oils cannot be chemically decomposed by alkalis, and must be removed by the action of surfactants. The metal surface is removed. In the process of degreasing, the surfactant molecules are first adsorbed on the interface between the oil and the solution. Under the action of the lipophilic and hydrophilic groups of the surfactant, together with the convection and stirring of the solution, the surface-active agent molecules will gradually disappear from the metal. The surface breaks off and enters the solution, forming an emulsion in the form of extremely fine balls. Of course, when using emulsifiers to remove oil, the temperature of the solution should not be too high, otherwise the surfactants will have salting out and lose their due effect.

2. Application in pickling and chrome plating

When the surface of the part is being strongly corroded by removing the oxide scale, various harmful gases are generated during the corrosion process, and acid mist is generated when the gas escapes, which has a great impact on the environment and equipment. If a small amount of OP emulsifier is added to the pickling tank, a layer of foam can be generated on the surface of the pickling solution to prevent the escape of acid mist. The current efficiency is extremely low during chrome plating (10%-15%), and insoluble lead anodes are used. After electrification, the two electrodes produce a large amount of hydrogen and oxygen, which is easy to produce harmful chromic acid fumes. Chromium mist not only pollutes the environment, endangers the health of operators, but also causes corrosion of equipment. In order to suppress the generation of chromium mist, a small amount of perfluoroalkyl ether sulfonate surfactant can be added to the chromium plating solution to form a layer of foam on the surface of the solution during chromium plating, which inhibits the escape of chromium mist and ensures the health of the operator. , And can reduce the consumption of chromic acid.

3. Wetting agent for plating solution

During the electroplating process, the metal ions are reduced at the cathode and accompanied by the side reaction of hydrogen evolution. With the progress of the hydrogen evolution reaction, the surface tension of the electroplating solution decreases and the wettability decreases. At this time, hydrogen bubbles tend to stay on the surface of the cathode. As a result, dents and pinholes appear in the deposited layer. In order to prevent the occurrence of this defect, a surfactant is added to the electroplating solution to reduce the interfacial tension between liquid-gas and liquid-solid, so that it is difficult for hydrogen bubbles to stay on the surface of the cathode. For example, a small amount of non-ionic surfactants such as oleyl alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether are added to the cyanide copper plating solution to prevent the occurrence of dents. Add a small amount of sodium lauryl sulfate anionic surfactant to the acid sulfate bright copper plating and weak acid sulfate bright nickel plating solution to prevent pinholes in the plating layer.

4. Brightener in bright plating solution

In acidic bright copper plating and acidic bright tin plating solutions, non-ionic surfactant polyethylene glycol (PEG6000) can be used as a primary brightener. The primary brightener can be adsorbed on the metal surface, which has an impact on the electrodeposition process, refines the crystal grains, and obtains a semi-bright coating. If the primary brightener is used in combination with other brighteners, a fully bright deposited layer can be obtained. Surfactant is added to the bright plating solution, and its dispersion effect can be used to obtain a bright deposited layer. For example, in the acidic stannous sulfate tin plating solution, the condensate of formaldehyde and o-toluidine is used as the brightener, and sodium octyl sulfate or nonylphenol polyoxyethylene ether is used as the dispersant, and full-bright tin can be obtained under stirring. Sedimentary layer. In the potassium chloride zinc plating solution, benzylidene acetone is used as the brightener, and sodium dinaphthalene methane disulfonate is used as the dispersant to obtain a bright zinc deposit. In order to obtain a bright, smooth, and finely crystalline deposited layer, a brightener must be added to the electroplating solution. Some brighteners are slightly soluble or insoluble in water. Using the solubilizing effect of surfactants, they can be dispersed into fine particles to be evenly distributed in the solution.