company news about Fundamentals of Electroplating

1.Electroplating Concept and Application
1.1. Definition of Electroplating
Electroplating is the process of applying direct current to a certain electrolyte solution and converting electrical energy to chemical energy to deposit metal onto the surface of a part.
 

1.2. Purpose of electroplating
By changing the appearance and physical and chemical properties of the surface of the parts, decorative, corrosion, and wear resistance can be achieved.
 

1.3. Application of Electroplating
Electroplating technology is widely used in automobiles, motorcycles, daily hardware, machinery, etc

2. Basic Terminology of Electroplating

2.1. Plating solution
Main salt, complexing agent, additional salt,buffers, etc.
 

2.2. Equipment
Plating tank, power supply, anode, cathode, etc.

Anode classification：

Insoluble anode: During the electroplating process, insoluble anodes do not dissolve and undergo oxidation reactions of certain substances on the surface, while the consumption of metal ions is supplemented by the addition of main salts.

Soluble anode: It refers to the production of anodes using plated metal materials, such as nickel for nickel plating and silver for silver plating. Anodic reactions are oxidation reactions of metals, generating metal ions to supplement the consumption of metal ions in cathodic reactions.                        

Cathodic reaction: The coated workpiece serves as the cathode, and the surface mainly undergoes a reduction reaction of metal ions (or their complex ions), forming a metal coating that covers the surface of the workpiece.

Rectifier: Provides the required current for electroplating. Most electroplating processes use DC power sources, and some electroplating processes use other types of power sources.

Plating tank: It is a utensil used to hold electrolyte. At the same time, it is necessary to meet the needs of cathode and anode installation, heating or cooling during the electroplating process.

3. Classification and Requirements for Electroplated Coatings

3.1. Classification of coatings

3.1.1 According to the purpose of use: Functional coating
                                                              Protective coating (zinc coating, cadmium coating, tin coating)
                                                              Protective decorative coating (Cu Ni Cr coating)

3.1.2 According to electrochemical relationship: Anodic coating
                                                                            Cathodic coating

3.1.3 Functional coating: Wear-resistant coating (hard chromium plating)
                                        Anti friction coating (tin plating, lead-tin alloy)
                                        Coating for hot working (preventing carburization and copper plating, preventing nitriding and tin plating)
                                        Solderability coating (tin plating, lead-tin alloy)
                                        Conductive coating (silver plated, copper plated)
                                        Magnetic coating (nickel plating, cobalt nickel plating, nickel iron plating)
                                        Repair coating (hard chromium plating, iron plating, copper plating)

3.2. Requirements for coating
3.2.1 Binding force
Matrix and coating, coating and coating
3.2.2 Coating coverage
Uniform coverage and no defects
3.2.3 Thickness
Thickness and porosity
3.2.4 Other indicators
Luminance, hardness, color, corrosion resistance, appearance

3.3. Factors affecting coating quality
3.3.1 Pre plating treatment
Oil removal, water washing, activation, acid corrosion, etc
3.3.2 Characteristics and condition of plating solution
Properties of plating solution, content of each component, etc
3.3.3 Condition of base metal
Electronegativity, charging into the slot, etc
3.3.4 Electroplating process
Current density, temperature, power transmission method, stirring, etc
3.3.5 Hydrogen evolution reaction
Pinholes, pits, blisters, hydrogen embrittlement, etc
3.3.6 Post electroplating treatment
Cleaning, passivation, hydrogen removal, polishing, etc
3.3.7 Electroplating power supply
Current, voltage, waveform, etc

4. Classification and performance of electroplating solutions

4.1. Classification of Electroplating Solutions
4.1.1 Single salt plating solution: chloride zinc plating
4.1.2 Complex plating solution: cyanide silver plating

4.2. Performance of plating solution
Dispersion ability: refers to the ability of the plating solution to evenly distribute the coating thickness, also known as the uniform plating ability.
Coverage ability: refers to the ability of the plating solution to deposit coatings on deep and concave surfaces of parts, also known as deep plating ability.
Current efficiency: refers to the ratio of the actual weight of the product to its electrochemical equivalent when passing through a unit of electricity on the electrode. Usually expressed as a percentage, expressed as“ η” Represent.

4.3. The influence of electroplating process conditions
4.3.1 Cathode current density: upper and lower limits of the range
4.3.2 Temperature: Range Highest and Lowest Temperature
4.3.3 Stirring: Cathode movement, air stirring, plating solution circulation
4.3.4 Power supply: power, waveform
4.3.5 Base metal: material properties, surface condition
4.3.6 Geometric factors: plating bath, anode, hanger, and parts

4.4. Factors affecting the distribution of coatings
4.4.1 Cathodic polarization: High cathodic polarization with good dispersion ability
4.4.2 Conductivity of plating solution: adding electrolyte
4.4.3 Cathode current efficiency: current efficiency, current density
4.4.4 Surface condition of substrate: smoothness, short-term impact current
4.4.5 Geometric factors: electrode shape, size, etc., shape of plating bath

5.Basic calculation of electroplating process

5.1. Tank liquid calculation
Total content of each substance=effective volume of tank liquid × Substance concentration (g/L) × Purity of the substance

5.2.Current efficiency calculation
5.2.1 Application of Faraday's Law in Electroplating
M=EQ/F=AQ/nF
M — the amount of material precipitated (or dissolved) on the electrode (g)
E — Molar mass of the substance (g/mol)
Q — The amount of charge passed through during electrolysis (C)
F — Faraday constant, 96500C/mol or 26.8Ah/mol
5.2.2 Current efficiency
η＝ (m,/m) × 100=100 × m, /(Itk)
η — Current efficiency (%)
m, — Mass of actual precipitated substance (g)
m — Calculate the theoretical mass value of the product according to Faraday's law (g)
I — Current passing through (A)
K — electrochemical equivalent
T — Time through current (h)

5.3. Calculation of electroplating time

t= ρ*σ/ (D η K)
ρ — Precipitation density (g/cm³)
σ — Coating thickness（ μm)
D — Current density (A/dm²)
K — Electrochemical equivalent (g/Ah)
η — Current efficiency (%)

5.4. Calculation of Electroplated Coating Thickness
σ＝ Dt η K/ ρ （μm)
D — Current density (A/dm²)
T — Time (min)
ρ — Precipitation density (g/cm³)
K — Electrochemical equivalent (g/Ah)
η — Current efficiency (%)