Introduction: Plastic electroplating can make the surface of plastic products have a metallic luster, beautiful, and play a decorative role; improve the mechanical strength of the surface of the product and extend the service life; make the plastic product have higher stability to external factors such as light and atmosphere, and not easy to age ; Make the plastic conductive, magnetic and weldable. Among them, the ABS process is the most mature and the electroplating effect is the best. This article shares the ABS electroplating process and its common problems, and the content is for your reference:
The main process flow of ABS plastic electroplating is: degreasing, roughening, sensitization, activation, electroless plating, electroplating, nickel plating, chrome plating, and finished products. In the above operation, the five steps before the electroplating operation are the electroless plating process, starting from the electroplating operation, it is the conventional electroplating process.
The main process flow of ABS plastic electroplating
The main purpose of degreasing is to degreasing and degreasing, while reducing its surface tension and giving its surface hydrophilicity. In the process of processing or transportation, the parts will inevitably be stained with oil, release agent and some sundries. These factors that affect the subsequent operations must be removed by degreasing operations. The degreasing operation has a certain effect on promoting uniform coarsening, improving the bonding force of the coating, and extending the service life of the coarsening liquid.
The purpose of roughening is to increase the surface roughness and increase the surface area to increase the bonding force between the metal coating and the plastic; make the surface of the plastic change from hydrophobic to hydrophilic, and all parts are evenly wetted by water to uniformly adsorb metal ions. The methods of coarsening include mechanical coarsening, solvent swelling coarsening and chemical coarsening.
The purpose of sensitization is to adsorb a layer of easily oxidized substances on the surface of the part so that the oxidation-reduction reaction can occur during the activation treatment and form a catalytic precious metal film on the surface of the part.
The purpose of activation is to first form a metal film on the surface of the part (adsorbing catalytic substances such as gold and copper on the surface of the sensitized part), which is used as a catalyst for the next chemical deposition, which is beneficial to electroless plating.
The so-called activation treatment is to immerse the part with the reducing agent in the solution containing the oxidant. Generally, it is immersed in a precious metal salt aqueous solution, and then the precious metal ions are reduced to precious metals by the reducing agent, thereby forming a precious metal film on the surface of the part. This layer of precious metal can play an active catalytic role, also called a catalytic film, which can accelerate the reduction reaction of electroless plating. Practice has proved that metals such as gold, silver, copper, and palladium all have this catalytic ability.
After the activation treatment, there is already a layer of silver or other metal film on the surface of the part, but because it is very thin, if it is immersed in an acid solution at this time, the silver film will peel off, so it is necessary to perform alkaline electroless copper plating first, and through oxidation-reduction reaction, A layer of copper is plated on the surface of the workpiece to strengthen the conductive layer, and then it can be electroplated in an acid medium. Electroless plating is an autocatalytic reduction reaction at low temperature. After the electroless plating is completed, enter the conventional electroplating process, and the parts can be electroplated like metal parts.
Solutions to common quality defects
The small bumps or bright spots on the surface of the plated part are caused by the deposition of small particles of solid impurities on the surface of the part. The cause may be impurity in the electroplating water, dirty or solid impurities in the electroplating tank. It is recommended to use deionized water in the electroplating process and strengthen the filtering effect; excessive coarsening can also cause pitting, and the concentration-temperature-time should be controlled. Relationship to prevent excessive coarsening.
The small pits on the surface of the plated part are mainly formed by the hydrogen absorbed on the surface of the part not being released in time during the electroplating process. The cause may be uneven air agitation in the electroplating tank. The air agitation should be improved to drive off the hydrogen adsorbed on the surface of the part.
The surface of the part is not plated, mainly because the front electroless plating is not deposited, causing the subsequent electroplating to fail. The cause may be that the electroplating bath is contaminated by the roughening solution or the electroless nickel reaction is not fast enough, and there is no partial deposition. The roughening solution should be prevented from being carried into the subsequent plating tank or the bath concentration should be increased.
The partial color of the surface of the plated parts is yellow. The main reason is that the chromium layer (silver white) of the part is not plated, and the color of nickel (white to yellow) is exposed. The cause is that the chrome plating current is too small, so the chrome plating current should be increased.
The sharp corners of the plated parts are protruding or rough, mainly due to the excessive current in the part of the part during the electroplating process, and the crystallization of the coating is rough. The electroplating current should be reduced.
The surface of the plated parts is corroded, discolored and tarnished, which is mainly caused by the poor corrosion resistance of the plated parts. The cause may be that the electroplating rack has poor electrical conductivity, resulting in insufficient electroplating film thickness and number of micropores, or the environment contains strong corrosive media, such as Cl, S and other substances. New racks should be made to improve the process to ensure the thickness of the electroplating layer and the number of micropores. And improve the environment.
Air bubbles are bulged on the surface of the plated part, which is mainly caused by the poor adhesion of the electroplated layer and the plastic layer. The cause may be poor material performance or excessive or poor roughening. Electroplating grade ABS should be selected or the roughening level should be appropriately reduced or increased.