Application of surfactants in electroplating industry

Surfactant industry is a new chemical industry derived from the development of oleochemicals and petrochemicals, and belongs to the category of fine chemicals. The surfactant industry has an inseparable and important relationship with the development of the national economy and the improvement of people's living standards. The application field of surfactants is very broad and is still expanding. Its influence and importance have attracted people's attention.


Surfactants in dilute solutions have the characteristics of adsorption, coordination, formation of micelles and reduction of surface interfacial tension to different interfaces. This produces multiple functions such as osmotic wetting, emulsification, dispersion, solubilization, foaming, and washing. Utilizing these functions in industry, agriculture, environment, and people's lives can achieve strange effects. Produce huge social and economic benefits.


Surfactants also have special effects in the electroplating industry. Its effect is manifested in the following aspects:


Broaden the application range of pH, temperature and current density of the electroplating solution; have good dispersibility to the metal particles precipitated in the electroplating, which is beneficial to improve the smoothness and brightness of the surface of the plating; reducing the surface tension is beneficial to the lubrication of the plating Wet; promote the rapid release of the hydrogen generated on the cathode surface to prevent dents and pinholes in the plated parts; the plating effect of the plated parts cleaned by surfactants is significantly improved. Can save power consumption.


According to foreign information, commonly used surfactants in the electroplating industry include: dioctyl succinate sodium sulfonate series (Aerosol); fatty alcohol sulfate series (Duponol); branched chain fatty alcohol sulfate series (Tergitol); Alkyl aryl sulfonate series (Nacconol); Alkyl naphthalene sulfonate series (Alkanol); Alkyl aryl phenol ether sulfate series (Triton 720); Fatty alcohol polyoxyethylene ether series (Triton NE); Polyoxyethylene nonylphenol ether series (Triton N).


Electroplating uses electrochemical principles to cover non-corrosive metals on the surface of other metals to prevent corrosion and achieve the purpose of protection and decoration. In order to achieve the goal of electroplating smoothly and obtain high-quality bright plated parts, it is usually necessary to remove oil and rust on the surface of the plated parts before plating. Add electroplating additives to the electroplating solution. Additives can be divided into complexing agents, leveling agents, impurity removal agents, brighteners, surfactants, etc. The most important of these are surfactants and brighteners.




Oil stains and other impurities are often attached to the metal surface, which affect the deposition of metal ions during electroplating. Therefore, the plated parts must be degreasing and derusting to ensure a good coating on the surface of the plated parts. Animal and vegetable oil can be treated with alkaline solution to remove oil stains. Oil, lubricating oil, petroleum jelly, anti-rust oil and other mineral oil stains can be removed by organic solvent method, chemical method and electrochemical method.




The most basic requirements for the electroplating wetting agent: better reduce the interfacial tension between the electrode and the plating solution; make the plating solution easy to spread on the electrode surface to achieve the purpose of even plating; the plating solution must have a certain degree of salt resistance and resistance Acid-base and temperature resistance, etc. The size of positive hydrophobic genes in surface active molecules has a great influence on wetting ability. When selecting an electroplating wetting agent, it is better to reduce the requirement of wetting power and to ensure its stability in the plating solution.




Additives refer to a small amount of substances that do not significantly change the electrical properties of the solution (conductivity, equilibrium potential, etc.) in the plating solution, but can significantly improve the performance of the plating layer.


Electroplating additives, such as complexing agents, brighteners, levelers, stress reducers, coating refiners, impurity removers, fog inhibitors, surfactants, etc. They generally have surface activity and are easily adsorbed on the interface of the electrode solution. It has a certain inhibitory effect on the discharge of metal ions, increases the cathode polarization, makes the metal deposition layer crystal fine, and improves the quality of the coating.




During the electroplating process, a fine and bright coating can be obtained after adding additives. This additive is called brightener. Brighteners can be divided into the following three categories: brighteners with obvious surface activity; brighteners with surface activity: it has surface activity but not obvious, its solution can not form micelles, can not be called surfactants, can be called surface Active substance; non-surface active brightener: this kind of brightener has no surface activity, but it is a very important brightener;




Surfactants used in the types of electroplating solutions include: zinc plating solution, copper plating solution, nickel plating solution, tin plating solution, chrome plating solution, etc.


Fog suppressant


During the electroplating process, the plated parts have to be pickled and derusted in advance to generate hydrogen. Hydrogen and oxygen are also generated during electroplating. These gases escape naturally entrained: acid mist, alkali mist, hydrogen mist, chromium mist and other harmful gases. They pollute the environment and poison the human body. Many of the most economical, effective and feasible methods to control fog damage are to use fog suppressants.


Requirements for surfactants for fog suppressants: The membrane wall must have a certain mechanical strength, elasticity and appropriate thickness for the bubbles generated. The liquid between the membranes must have a certain viscosity to withstand the collision between bubbles/bubbles and bubbles/plating parts. Acid resistance, alkali resistance and certain temperature resistance; good chemical stability. It is resistant to oxidation, reduction and cyanide without chemical reaction; the foam layer is kept at a thickness of 20-30min. If it is too thick, excessive hydrogen and oxygen will accumulate, which will cause explosions in case of fire.