Brass and zinc plating are two common industrial finishing processes used to coat metal surfaces. But which one is better? Here is an in-depth comparison of brass plating vs zinc plating in terms of composition, durability, corrosion resistance, appearance, cost, and applications.
Brass Plating vs Zinc Plating: Key Differences
Composition
- Brass plating involves depositing a layer of brass onto a metal substrate. Brass is an alloy composed of copper (around 60-80%) and zinc (20-40%). The properties of brass can vary based on the exact ratio of copper to zinc.
- Zinc plating entails coating the base metal with a layer of zinc metal. Zinc coatings are typically 99% pure zinc or zinc alloys with small amounts of other metals such as nickel or cobalt.
- With brass plating, the plating layer is 100% brass alloy. But for zinc plating, the plating layer is nearly pure zinc.
- The core material under the plating differs too. Brass coatings are commonly layered over steel, zinc, or copper substrates. Zinc platings are primarily applied to iron and steel.
Durability
- Brass is harder and stronger than zinc. The hardness of brass plating enhances the wear resistance of the underlying metal.
- Zinc is a relatively soft metal. Zinc platings provide good corrosion resistance but lower wear resistance.
- Brass platings tend to be thicker than zinc coatings. Standard brass plating thickness ranges from 0.0003 to 0.002 inches. Zinc platings are usually between 0.0002 and 0.001 inches thick. The greater thickness provides brass coatings with higher durability.
- When brass plating wears through, the stronger brass alloy underneath provides continued protection. Zinc coatings over steel have less abrasion resistance when the zinc layer is compromised.
Corrosion Resistance
- Brass and zinc both provide excellent corrosion protection for steel and other metals. This is a key benefit of both plating processes.
- Zinc platings typically provide longer corrosion protection than brass in severe environments, like marine applications. The sacrificial protection of zinc coatings gives them an advantage concerning corrosion.
- In less harsh conditions, brass platings can match or exceed the corrosion performance of zinc. Brass holds up better against corrosion from chemicals, water, and outdoor weathering.
- If the brass plating layer gets damaged, the zinc or steel underneath will be more susceptible to corrosion than with a zinc plating over steel.
Appearance
- Brass platings really shine when aesthetics matter. Brass has an attractive golden color and can be buffed to a brilliant finish. Different etching processes can produce antique and artistic effects.
- Zinc has a grayish, dull sheen. It provides functional corrosion protection but with a plain industrial look. Zinc coatings are not used for decorative purposes.
- Brass coatings can be left with a soft satin luster or polished to a mirror-like shine. This versatility makes brass an ideal plating metal for consumer products and decorative hardware.
Cost
- Brass plating is generally more expensive than zinc plating. The cost difference stems from the higher material price for brass compared to pure zinc.
- Labor and processing costs for brass and zinc plating are similar. But the brass alloy itself costs more than zinc metal.
- Brass platings tend to be thicker than zinc, which also adds to the material cost. Thicker platings require longer processing times as well.
- However, brass platings frequently last longer than zinc coatings, offsetting some of the higher initial cost over time. Less frequent re-plating ultimately saves money.
Common Applications
Brass Plating Uses
- Decorative finishes on fixtures, furniture hardware, door handles, and other consumer products
- Plating for musical instruments and other specialized equipment
- Corrosion protection for marine components like fasteners, instruments, and valves
- Enhanced wear resistance on valves, gears, and bushings
Zinc Plating Applications
- Corrosion protection on automotive parts, fasteners, brake components, tools, and construction materials
- Coatings for outdoor steel structures like fences, railings, transmission towers, and more
- Functional industrial plating with corrosion/abrasion resistance
- Undercoating below paints and powder coatings
As this overview shows, brass and zinc platings each have advantages depending on the application and intended use.
How Brass Plating Works
Brass electroplating involves using an electrical current to bond a thin layer of brass alloy onto a metal part, most commonly steel or zinc. This is an electrochemical process where brass ions dissolved in a plating solution deposit onto the positively charged part.
Here are the key steps in the brass plating process:
Surface Preparation
The part surface must be thoroughly cleaned to remove oils, oxides, and other contaminants. Alkaline or acid baths are often used to clean and etch the surface. This helps the brass coating bond tightly.
Activation
The part acts as the cathode (negative electrode) in the electroplating setup. An electrical current is used to activate the surface, creating a negative charge. This prep step primes the metal for brass deposition.
Plating
The negatively charged part is immersed in a brass plating bath along with a positively charged anode. When a current is applied, brass ions in the solution are drawn to the cathode. The brass builds up evenly across the surface.
Rinsing
After plating to the desired thickness, the part is removed from the plating bath and rinsed thoroughly. This prevents chemical carryover that could cause staining or other defects.
Finishing
Finally, the plated parts may go through additional finishing steps like brushing, buffing, lacquering, or waxing. This enhances the appearance and luster of the finished brass plating.
The thickness of the brass plating depends on the length of time in the plating bath. Brass platings usually range from 0.0003 to 0.002 inches thick. Multiple layers may be applied to increase durability.
How Zinc Plating Works
Zinc electroplating uses a similar process but with a pure zinc plating solution rather than a brass alloy.
Here are the basics steps:
Cleaning
The parts must be cleaned and degreased before plating to get a good zinc deposit. Alkaline cleaners help remove oils and dirt.
Activation
The parts are made the cathode via electrical contact points in the tank. An electrical current activates the surface to attract zinc ions.
Zinc Plating
With current flowing, the parts are lowered into the zinc plating bath. The positively charged zinc ions attach to the cathodic part surfaces.
Rinsing
After plating, the parts are thoroughly rinsed just like with brass plating. Rinsing prevents chemical residues from causing problems.
Drying
Finally, the zinc plated parts are dried either with hot air or in an oven. This prevents water spots from marring the surface.
Zinc electroplating allows for fine control over coating thickness. Typical zinc platings range from 0.0002 to 0.001 inches thick. Zinc coatings are generally thinner than brass platings.
Pros and Cons of Brass vs Zinc Plating
Brass Plating Pros
- Excellent appearance – from satin to polished
- Greater hardness and wear resistance
- Provides good corrosion protection
- Ideal plating for decorative applications
- Higher durability than zinc platings
Brass Plating Cons
- More expensive than zinc plating
- Lower sacrificial corrosion protection than zinc
- Softer than other alloys like nickel or chrome
Zinc Plating Pros
- Low cost zinc coatings
- Cathodic/sacrificial protection from corrosion
- Easy to apply thin, uniform platings
- Electrically conductive coatings
Zinc Plating Cons
- Provides less abrasion resistance
- Dull gray appearance lacks aesthetic appeal
- Shorter lifespan than some other platings
- Brittle coatings prone to cracking
Choosing Between Brass vs Zinc Plating
So when trying to choose between brass or zinc plating, consider these key factors:
Appearance – Brass if decorative finishes are needed, zinc for purely functional coatings.
Corrosion Resistance – Zinc provides better galvanic/sacrificial protection. But brass also offers good corrosion resistance.
Wear Resistance – Brass platings have an advantage in hardness and abrasion resistance.
Cost – Zinc is the more economical plating option.
Applications – Brass for marine components, musical equipment, consumer products. Zinc for automotive parts, tools, construction materials.
Analyze your specific needs in terms of use environment, required durability, appearance, and budget. In many cases, zinc makes sense for industrial applications where cost and corrosion protection are paramount.
For long lasting decorative platings, brass is hard to beat. Its warm golden shine and ability to take a mirror polish make brass an unrivaled plating choice for upscale fixtures, hardware, and quality consumer products.
References
[1] American Plating Power. “Brass Plating vs Brass Coating: What’s the Difference?” https://www.americanplatingpower.com/brass-plating-vs-brass-coating-whats-the-difference/
[2] Sharretts Plating Company. “Zinc Electroplating.” https://www.sharrettsplating.com/zinc-electroplating/
[3] Aalberts Surface Technologies. “The Zinc Plating Process.” https://www.aalberts-st.com/processes/metal-finishing-technologies/zinc-plating
