Zinc Plating
Keep your parts from corroding while improving their appearance.
A More Environmentally Friendly Way to Fight Corrosion
Zinc plating began to see wider adoption in the 1980s as an alternative to cadmium coatings to prevent corrosion on steel parts. It’s generally regarded as a greener alternative since the plating solution is less toxic to the environment when compared to cadmium.
What is Zinc Plating?
Zinc plating is a subcategory of electroplating, which refers to the use of an electric current to dissolve a metal, in this case zinc, in a solution bath for the purpose of forming a metal coating on a part.
Zinc plating may be conducted to enhance a product’s corrosion control characteristics, or as an aesthetic finish for small parts that may be visible on a fully assembled product.
How the Zinc Plating Process Works
1. Surface Preparation
Before beginning the plating process, any debris or contaminants that remain on the surface of the parts must be removed to ensure consistent adhesion of the zinc coating. The cleaning process usually occurs in two steps: first, we apply an alkaline detergent solution, and then we apply an acid treatment to remove any surface rust (this is often referred to as “pickling”).
2. Plating Solution Preparation
The parts will be immersed in an electrolyte solution that we refer to as the plating bath, which consists of the zinc metal ionic solution and other chemicals that aid the plating process.
3. Introducing the Electrical Current
This process is a type of electroplating, which means that an electrical current is used to deposit metal ions onto the part’s surface.
4. Post Treatment Procedures
After the electrical current is run through the parts in the solution, they are rinsed with water to remove contaminants and then thoroughly dried. If your parts require extra corrosion protection, we can then apply additional passivates and sealers.
Zinc Plating at Paulo
Our high-capacity plating operations feature:
- Trivalent chromates including clear and yellow, but never toxic hexavalent chromates
- Seals to improve salt spray performance
- Large baking operation to reduce the risk of hydrogen embrittlement
- RoHS 2 and REACH compliance
- Available compliance with many auto industry OEM plating specifications
Lot Sizes and Part Types
Zinc plating is traditionally performed on large batches of small parts, so manufacturers looking to contract out this important service will want to make sure they’re working with a partner that has the capacity to handle large volumes of parts. At Paulo, our lines are capable of delivering quality plating work at a rate of 12,000 pounds per hour, with turnaround times that fit with your schedule. Parts we commonly apply zinc plating to include:
- Screws
- Fasteners
- Nuts
- Bolts
- Other small hardware pieces
Zinc Plating FAQs
Can you remove zinc plating?
Yes it is possible to remove zinc plating. At Aalberts Surface Technologies – Paulo, we can strip and re-plate parts that were originally plated in our facility.
Do my parts need hydrogen embrittlement relief?
Hydrogen embrittlement relief is a post-plating heat treatment that drives out hydrogen absorbed during the cleaning and plating process. Parts with a hardness above HRC 32 typically require this step to prevent potential brittleness and stress cracking. We perform HE relief treatment, but we don’t guarantee complete elimination of all hydrogen embrittlement risk.
Do parts need to be clean before zinc plating?
Absolutely. Parts must arrive clean and free of oils, greases, heavy rust, and other contaminants. While we do perform cleaning as part of our standard process, heavy contamination can prevent proper plating adhesion and cause coating defects. Clean parts ensure uniform, high-quality zinc coating across all surfaces.
How thick is zinc plating?
We can produce zinc plating conforming to four classes specified in ASTM B 633: Fe/Zn 5 (5 microns), Fe/Zn 8 (8 microns), Fe/Zn 12 (12 microns), and Fe/Zn 15 (15 microns). The number indicates the coating thickness in microns. Thicker coatings generally provide longer corrosion resistance, but they also increase cost and processing time.
What is zinc plating?
Zinc plating is an electrochemical process that deposits a thin layer of zinc onto steel parts to provide corrosion resistance. Unlike galvanizing, which mechanically applies or dips parts in molten zinc, zinc plating uses electrical current in a conductive solution to create a more uniform, adherent coating.
What size parts can you zinc plate?
Our barrel plating process works best for small parts—fasteners, nuts, bolts, clips, small brackets, and similar hardware. Barrel plating works by rotating the parts in a perforated barrel during plating, which gives small parts a more consistent coating than rack plating.
What testing is available for zinc plated parts?
Our Murfreesboro Division offers in-house salt spray testing, which saves you a critical step in quality control. Salt spray testing verifies how long your plated parts can resist corrosion in controlled humidity chamber conditions. We can also test coating thickness and perform other quality checks as specified in your requirements.
Will zinc plated parts rust?
Eventually, yes. The zinc coating is essentially corrosion itself. It acts as a sacrificial layer that corrodes preferentially to the underlying steel, protecting your parts for a period of time. How long they resist corrosion depends on the coating thickness, passivation type, and whether you apply additional sealers. Standard passivated zinc plating typically passes 48-72 hours of salt spray testing. With sealers, we can achieve 300+ hours or even 500+ hours for specialized applications like automotive wheel weights.
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