Parts are subjected to various stresses in actual applications. It may be corroded by other parts, chemicals, solvents, or the environment. Parts may also wear out faster during operation because it may be subjected to wear or friction.
In order to extend the service life of the part and prevent corrosion, another metal material can be plated on the part. This plating process is called electroplating. Using electrolysis, a thin layer of another metal is electrically attached to the surface of the part. In addition to providing corrosion resistance and enhanced wear resistance, electroplating can also enhance the performance of the part, make it more durable, or improve its appearance.
Many types of metals can be used in the electroplating process. Nickel, chromium, and zinc are widely used, depending on the industry and purpose of the part. Each metal has its advantages and disadvantages. Let's take a look at the differences between zinc plating, chrome plating, and nickel plating.
Zinc plating
In addition to being resistant to alkalis, sulfides, and acids, zinc plating also has excellent corrosion resistance. This metal also has good mechanical strength. Because it is a stable metal, it is often used in humid and high temperature environments. Since zinc resources are abundant and easy to process, the cost is low. However, it should be noted that galvanizing is not suitable for parts with high friction. It is often used in many applications to prevent parts from rusting.
Typical applications:
Anti-corrosion of steel parts: such as automobile bolts, scaffolding, and outdoor hardware (using the sacrificial anode protection of zinc to preferentially corrode the zinc layer to protect the substrate).
Low-load parts: such as springs and gaskets (low cost but not wear-resistant).
Advantages and disadvantages:
High cost performance, suitable for large-scale anti-corrosion needs;
Low hardness, not suitable for friction scenes, easy to oxidize at high temperatures (zinc melting point 419℃).
Nickel plating
Nickel plating is a hard material with good corrosion resistance. It is usually plated on copper to enhance the natural corrosion resistance of copper. Nickel is also highly reflective and is used for decorative purposes. This metal can enhance the appearance of metals and improve wear resistance. Nickel is a porous metal, so multiple layers must be plated on other metals to provide protection.
Typical applications:
Decorative plating: such as bathroom hardware, automotive interior parts (bright nickel + sealing to improve aesthetics).
Functional coating: electronic components (nickel has medium conductivity and can be used as pad bottom layer), mold surface (increases hardness and corrosion resistance).
Composite coating: forms nickel-phosphorus alloy with phosphorus, carbon, etc. (amorphous structure, higher hardness).
Advantages and disadvantages:
Good gloss, acid corrosion resistance (such as organic acid resistance);
High cost, too thick and easy to embrittle, need to be matched with copper layer to prevent hydrogen embrittlement.
Chrome plating
Chromium is very stable when exposed to certain acids, carbonate sulfides, alkalis and humid climates. This metal has high heat resistance, good wear resistance and hardness. Chrome plating can provide parts with good wear resistance and light reflection advantages. However, chromium is very brittle and porous. Chromium itself does not provide good corrosion protection. However, when it is combined with copper and nickel, this coating can be used for parts in corrosive environments.
Typical applications:
Decorative chrome plating: car wheels, furniture handles (mirror effect, improve grade).
Hard chrome plating: mechanical shafts, piston rings, molds (high hardness + wear resistance, repair of worn parts).
Special uses: aerospace parts (resistant to high temperature oxidation, chromium melting point 1857℃).
Advantages and disadvantages:
Highest hardness, extremely strong wear and corrosion resistance;
High environmental protection cost, complex process (current density needs to be strictly controlled), and the coating is easy to crack (thick coating needs stress relief treatment).
In addition to these metals, cadmium, copper and tin plating can also be used for industrial parts. Precious metals such as gold, silver and platinum can also be used for electroplated parts. Gold is a common plating for semiconductors and connectors in the electrical and electronic industry.
How to choose?
When choosing a metal plating for your part, consider the use of the part in the actual application and whether it will interact with the environment. Then choose a plating that provides corresponding advantages.
Consider corrosion protection and cost: choose zinc plating (such as outdoor steel parts).
Need decorative and medium corrosion resistance: choose nickel plating (such as home appliance housing, sanitary products). Pursuing high hardness and wear resistance: Choose chrome plating (such as mechanical transmission parts, molds).
Complex requirements: Combined plating (such as copper + nickel + chrome, taking into account adhesion, gloss and hardness, used for car wheels).