Basic electroplating process flow

Pre treatment: All processes before plating are called pre-treatment, which aims to repair the surface of the workpiece

1、 Basic process

(Polishing → Polishing) → Hanging → Degreasing and degreasing → Water washing → (electrolytic polishing or chemical polishing) → Acid washing activation → (pre plating) → Electroplating → Water washing → (post-treatment) → Water washing → Drying → Hanging → Inspection of packaging

2、 The role of each process

1. Pre treatment: All processes before plating are called pre-treatment, which aims to repair the surface of the workpiece, remove grease, rust, oxide film, etc., and provide the required plating surface for subsequent coating deposition. Pre treatment mainly affects appearance and adhesion. According to statistics, 60% of electroplating defects are caused by poor pre-treatment, so pre-treatment plays a very important role in electroplating processes. In countries with advanced electroplating technology, pre-treatment processes are highly valued, accounting for half or more of the entire electroplating process. As a result, coatings with good surface conditions can be obtained and the defect rate can be greatly reduced.

Sandblasting: Remove rust, welding slag, carbon deposits, old paint layers, and other dry oil stains from the surface of parts Remove the molding sand and oxide scale on the surface of castings, forgings, or heat-treated parts Remove burrs and directional wear marks on the surface of the parts Reduce the roughness indicated on the parts to improve the adhesion of paint and other coatings Make the parts in a diffuse reflection extinction state

Polishing: Remove various macroscopic defects such as burrs, rust, scratches, welds, weld beads, sand holes, oxide scales, etc. indicated on the parts to improve the flatness and electroplating quality of the parts.

Polishing: The purpose of polishing is to further reduce the roughness of the surface of the part and obtain a shiny appearance. There are mechanical polishing, chemical polishing, electrochemical polishing and other methods available.

Degreasing and degreasing: Remove the grease from the surface of the workpiece. There are methods such as organic solvent degreasing, chemical degreasing, electrochemical degreasing, wiping degreasing, and drum degreasing.

Acid washing: Remove rust and oxide film from the surface of the workpiece. There are chemical pickling and electrochemical pickling.

2. Electroplating

Obtaining the required coating on the surface of the workpiece is the core process of electroplating, and the quality of this process directly affects the various properties of the coating. The factors that have a significant impact on the coating in this process mainly include the following aspects:

① Main salt system

Each plating type will develop multiple main salt systems and corresponding additive systems. If galvanized, there are systems such as cyanide galvanizing, zincate galvanizing, chloride galvanizing (also known as potassium salt galvanizing), ammonium salt galvanizing, sulfate galvanizing, etc.

Each system has its own advantages and disadvantages, such as good dispersion and depth ability of cyanide zinc plating solution, fine crystallization of coating, good adhesion with substrate, good corrosion resistance, wide process range, stable and easy operation of plating solution, and less sensitivity to impurities. But it is highly toxic and seriously pollutes the environment. Chloride zinc plating solution is a single salt plating solution without chelating agents, and wastewater is easily treated The brightness and flatness of the coating are superior to other systems High current efficiency and fast deposition rate Steel with low hydrogen overpotential, such as high carbon steel, castings, forgings, etc., are prone to plating. However, due to the weak acidity of chloride ions, they have a certain degree of corrosiveness to the equipment. On the one hand, they can cause certain corrosion to the equipment. On the other hand, this type of plating solution is not suitable for deep holes or tubular parts that require auxiliary anodes.

② Additives

Additives include gloss agents, stabilizers, softeners, wetting agents, low zone displacement agents, etc. Glossing agents are divided into main gloss agents, carrier gloss agents, and auxiliary gloss agents. For the same main salt system, using additives made by different manufacturers can result in significant differences in the quality of the resulting coatings. Overall, additives from developed countries such as Europe, America, and Japan are the best, followed by Taiwan, while those produced in mainland China are relatively inferior to the first two categories.

The combination of the main salt and a specific manufacturer's additive determines the overall performance of the plating solution used. Excellent additives can compensate for certain performance deficiencies of the main salt. The deep plating ability of the plating solution obtained by combining excellent chloride zinc plating additives with chloride main salts is better than that of many cyanide zinc plating solutions.

③ Electroplating equipment

(1) Hanging fixtures: Square hanging fixtures are used in conjunction with square plating tanks, while circular hanging fixtures are used in conjunction with circular plating tanks. circular

Shaped plating tanks and hanging fixtures are more conducive to ensuring uniform current distribution, while square hanging fixtures require adding current dispersing devices such as wire mesh around the hanging fixture or shortening the length of the anode plates on both sides, using an elliptical anode arrangement as shown in the figure.

(2) Stirring device: promotes the flow of the solution, evenly distributes the solution state, and eliminates the residence of bubbles on the surface of the workpiece

(3) Power supply: DC, good stability, low ripple coefficient.

3、 Post processing

After electroplating, various treatments are carried out on the coating to enhance its various properties, such as corrosion resistance, anti discoloration ability, weldability, etc.

Dehydration treatment: Adding a dehydrating agent to the water, such as post-treatment with bright nickel plating

Passivation treatment: Improve the corrosion resistance of the coating, such as galvanizing

Anti discoloration treatment: Add anti discoloration agents to water, such as silver plating, tin plating, imitation gold plating, etc

Improve solderability treatment: such as tin plating

Therefore, the quality of the post-treatment process directly affects the performance of these coating functions.