Zinc Plating
Industrial zinc plating is the process of applying a protective zinc coating to steel parts to provide corrosion resistance and maintain tight tolerances. That's the definition, but plating isn't the hardest part. Getting complete coverage, long-lasting protection, and on-time delivery takes experience.
At Gatto, we run rack and barrel zinc daily, help teams understand finish requirements, and plate oversized parts up to 27 feet on the largest zinc plating line in the U.S. All done in our Chicago facility for speed, consistency, and reliability.
Zinc Finishes We Offer
We offer a full range of zinc electroplating services, with finishes available through both rack and barrel processing.
Gatto's Zinc Plating Chromates
| Zinc | Barrel | Rack | Salt Spray | Common Specifications |
|---|---|---|---|---|
| X | X | Up to 12 Hrs | ASTM B 633 Type III | |
| High Corrosion Clear Trivalent | X | X | Up to 120 Hrs | ASTM B 633 Type V |
| Yellow Trivalent | X | X | Up to 120 Hrs | ASTM B 633 Type VI |
| Yellow Hexavalent | X | X | Up to 96 Hrs | ASTM B 633 Type II |
| Black Trivalent | N/A | X | Up to 120 Hrs | ASTM B 633 Type VI |
| Black Hexavalent | X | X | Up to 72 Hrs | ASTM B 633 Type II |
| Olive Drab Hexavalent | X | X | Up to 96 Hrs | ASTM B 633 Type II |
We also offer Zinc-Nickel Plating which provides up to 10 times the protection of conventional zinc plating
What Sets Our Zinc Plating Apart
We're set-up to plate parts that many shops can't, like large electronic enclosures, high-volume stock, or complex assemblies with tight requirements. Our process is designed to keep production moving and results consistent, regardless of the part or the order size. Here's how:
Oversized Parts Up to 27 Feet -KING KONG Line
Plate long or heavy parts without sectioning or redesigning around tank limitations, eliminating weld seams, extra handling, and unnecessary costs.
Our Process. Tailored to your Part.
We adjust how we run each job to maximize plating coverage and achieve more uniform thickness across features.
High-Throughput Barrel Line
Our 31-station barrel line is built for volume, with skilled operators and process monitoring to maintain consistency across orders.
Plated to Your Requirements
We work with manufacturing specifications everyday, ensuring what’s on the print is what gets applied to your parts.
In-House Baking with 10 Ovens
We bake parts immediately after plating to prevent hydrogen related failures, with large capacity batch ovens and clear documentation with every order.
Capacity That Keeps Jobs Moving
We’re built to move volume, with most orders shipping within 5 business days or less.
Where Zinc Plating Works Best
Zinc electroplating is one of the most widely used, versatile, and cost-effective finishes in manufacturing. It provides reliable protection and offers tight dimensional control for a wide range of part types. Depending on the chromate selection and plating thickness, zinc finishes can meet or exceed salt spray performance across industries.
Ideal When You Need:
- Scalable corrosion resistance, from mild indoor exposure to more demanding service conditions, depending on coating thickness and chromate type.
- Good electrical conductivity
- Reliable adhesion for post- plate painting, powder coat or other secondary coatings
Common Applications:
- Fasteners, brackets, and small components
- Welded assemblies, stamped parts, and fabricated sheet metal
- Slotted channel, tubing, and hardware
- Used across telecom, infrastructure, manufacturing, and OEM supply chains
Need greater corrosion protection? Consider Zinc-Nickel Plating.
Need Help with a Specification?
ASTM B633 is the most common zinc plating specification, and one we work with every day.
Whether your print clarifies the details or just states "Zinc per ASTM B633," we can help you interpret what's required. From chromate type and plating thickness to service condition and performance expectations, we work with you to ensure your finish meets both compliance and functional requirements.
Plating Requirements: What to Include
A complete finish callout helps us process your parts correctly the first time, avoiding delays, rework, or unexpected results. Whether you're developing a new drawing or requesting plating for an existing part, the more detail we have upfront, the faster we can move your order through production.
Key Details to Include:
- Plating Type - Zinc or Zinc-Nickel
- Coating Thickness - If specified, include the required thickness. If not, share the part's use and environment so we can suggest appropriate options based on specifications.
- Chromate Type and Color -
- Type: Trivalent or Hexavalent
- Color: Clear, Yellow, Black, or Olive
- Additional Requirements - Baking, rust preventive, sealers, special handling or packaging, etc.
If you're unsure about the details, our team can review your drawing or answer any questions to help determine the best approach for your parts. Contact us.
Trivalent vs. Hexavalent Chromates: What's The Difference?
A chromate conversion coating is a thin chemical layer applied over zinc plating to protect the finish and define its final appearance. Available in clear, yellow, black, or olive drab.
Why It Matters in Zinc Plating
Chromates are a key part of a complete zinc finish. They prevent the zinc layer from breaking down, extending corrosion resistance, improving salt spray performance, and lengthening part life. The choice between trivalent and hexavalent determines compliance, performance, and where the part can be used.
Hexavalent Chromates (Non-RoHS Compliant)
- Also called dichromates
- Excellent corrosion resistance
- Not RoHS Compliant -Contains hexavalent chromium
- Still used in military, aerospace, or general industrial applications that don't stipulate RoHS compliance
Trivalent Chromates (RoHS Compliant)
- Most common option today
- RoHS Compliant -free of hexavalent chromium
- Provides good protection, though hexavalent generally offers higher corrosion resistance in most cases
- Preferred by most OEMs as a replacement for hexavalent coatings
Whether you're working from an old drawing or making a finish decision, it's important to know how chromate type affects performance, compliance, and long-term protection. We plate with both and can help clarify what your specification requires or recommend the right option for your application.
Understanding the Zinc Finish Structure
A zinc finish consists of two main layers, zinc and chromate, each serving a distinct purpose in corrosion protection, durability, and finish appearance.
Zinc Plating - Sacrificial Protection
Zinc is applied through electroplating, forming a thin metallic layer that will corrode before the underlying steel, offering sacrificial protection to the surface.
Zinc Thickness - Why It Matters
The thicker the zinc layer, the longer the protection. Most specifications define a minimum plating thickness, either stated directly (in microns or inches) or assigned through a code. ASTM B633, for example, defines zinc thickness by class:
- Fe/Zn 5 = 5 microns
- Fe/Zn 8 = 8 microns
- Fe/Zn 12 = 12 microns
Other industry standards follow the same principle: a defined minimum thickness ensures the finish provides the required level of corrosion resistance.
Salt spray testing is often used to verify performance, but it does not directly determine thickness. Instead, salt spray hours act as a durability benchmark when paired with the specified zinc thickness and chromate type.
Post-Plate Baking - Hydrogen Embrittlement Relief (When Required)
The electroplating process generates hydrogen at the surface of the part, which can make high-strength steels brittle and prone to failure in use. To reduce this risk, parts are baked after plating to drive out hydrogen and relieve stress. Bake requirements are typically determined by the hardness of the base material and are applied before chromating when needed.
Chromate Coating - Final Appearance and Additional Protection
After baking (if needed), a chromate conversion coating is applied. It improves durability, adds corrosion resistance, and defines the final appearance.
What Salt Spray Hours Mean in Zinc Plating
Salt spray testing helps compare how different finishes resist corrosion. It doesn't predict exact lifespan, but it gives a performance baseline:
- A finish rated for 120 hours offers stronger resistance than one rated for 12, and typically performs better during transit, storage, or mild exposure.
Is Zinc Electro Plating the Same as Galvanizing?
Zinc electroplating is a form of galvanizing, also called electrogalvanizing. Galvanizing is the general term for applying a zinc coating to steel or iron to prevent corrosion, which can be done by several methods including electroplating, hot-dip galvanizing, mechanical plating, and thermal spray.
The Most Common Mix-Up: Electroplating vs. Hot-Dip Galvanizing
In practice, "galvanizing" most often refers to hot-dip galvanizing.
- Zinc electroplating uses an electrolytic process to apply a thinner, more controlled layer of zinc. Ideal for parts with threads, tight tolerances, or complex geometries where dimensional control is critical.
- Hot-dip galvanizing immerses steel into molten zinc, creating a much thicker, durable coating-commonly used for structural steel or outdoor environments.
Coverage Limitations in Zinc Electroplating
Zinc electroplating works through an electrolytic process, requiring a direct line-of-sight between the anode and the surface being plated.
What This Means for Your Parts
- Interior areas - such as deep recesses, enclosed weldments, corners, or inside tubing, may receive little to no zinc coverage during the standard plating process.
- Interior coverage can be improved with custom racking, auxiliary anodes, or other special setups.
Because these accommodations require extra handling and setup time, they can increase both cost and lead time. Since they are not part of our standard process, the need for interior coverage should be communicated upfront to ensure correct processing and pricing.
ASTM B633 and "Significant Surfaces"
The ASTM B633 zinc plating specification addresses this interior coverage limitation by defining significant surfaces as areas where corrosion protection is required and reasonably accessible during plating. Fully enclosed or recessed areas are not typically considered significant surfaces and usually not required to meet minimum plating thickness requirements.
Our Recommendation
If you're unsure how your part will plate, send us a drawing or sample. We'll evaluate it before production and let you know if special setups are required to achieve the desired results.
Zinc plating is a functional finish and will not hide imperfections. It's a thin electrolytic coating that replicates the condition of the base metal and won't fill in scratches, welds, or surface
What to Expect:
- Surface defects such as weld marks, deep scratches, pitting, or porosity will remain visible after plating.
- In some cases, imperfections may appear more noticeable once plated.
- Uniform or cosmetic finishes may require pre-plate prep (polishing, blasting) or post-plate finishing.
Why It Matters
The appearance and performance of the coating depend heavily on the quality of the base metal.
For the best results, parts should be free of surface defects before plating. Different chromates (clear, yellow, black, olive) can change the color of the finish, but won't conceal imperfections.
Zinc electroplating adds approximately 0.0002"-0.0010" of thickness, depending on the specification and performance required. While the process is controlled, maintaining a final tolerance tighter than ‡0.0004" is not practical due to inherent variation.
Plating should not be relied upon to correct undersized parts; base dimensions should be within tolerance before coating, with allowance made for the specified thickness. Incorporating this allowance during design and quoting helps ensure parts meet functional requirements after plating.
Zinc Plating: Quick Answers to Common Questions
ASTM B633 is the most widely used zinc electroplating specification, defining coating thickness, chromate type, and corrosion protection for steel parts. It's a reference engineers and OEMs use to ensure finishes meet both compliance and performance requirements.
Trivalent chromates are RoHS compliant and widely accepted for most industries, while hexavalent chromates are non-RoHS compliant. Trivalent has become the standard for most industries, but hexavalent is still used in many defense and general industrial applications.
No. Standard zinc electroplating cannot fully coat interiors of tubes or enclosed recesses because the process requires a direct electrical path between the anode and surface. Limited coverage in these areas should be expected, and full interior plating (if possible at all) will require custom racking auxiliary anode, or other special modifications.
No. Zinc plating does not hide defects, it replicates the surface of the base material. Scratches, welds, porosity, or pitting remain visible after plating. For a more uniform appearance, pre-plate prep (such as polishing or blasting) or secondary finishing may be required.
Most zinc plating specifications call for a minimum thickness between 0.0002" and 0.0010" (5-25 microns).
In practice, our process can typically hold a range of about 0.0004", so a part with a 0.0002" minimum might measure between 0.0002" and 0.0006".
Achieving tighter tolerances is sometimes possible, but often requires smaller batch sizes and defining specific areas where uniformity is critical. It's also important to note that plating thickness naturally varies: edges and sharp features usually build up faster (high current density), while recessed or shielded areas tend to build slower (low current density).
Yes. Zinc plating is RoHS compliant when finished with trivalent chromates. Hexavalent chromates are not RoHS compliant.
Yes. But usually as a base layer rather than a standalone finish. In harsher environments, zinc plating is often paired with a secondary coating such as paint to provide longer-lasting protection. This combination has been used in applications like suspension bridge components, structural hardware, and electrical enclosures.
When zinc alone is used outdoors, the finish will eventually break down, leading to appearance changes and reduced protection.
For applications that demand greater protection, zinc-nickel plating offers enhanced durability over zinc.
Located in Chicago, we reach 65% of the U.S. in a day, lowering freight costs, reducing lead times, and enabling direct shipping to your customer.
With 210,000 sq. ft., we process full truckload orders efficiently, keeping parts organized and on schedule with dedicated staging, processing, and tracking.
Flaking, bleed-out, poor adhesion, we catch plating issues early before they turn into costly problems.
From fast quotes to clear answers, we simplify the plating process so you can focus on the rest of your project.
Contact Our Plating Experts
Whether you know exactly what you need or just need to talk it through, we’re here to help with quick turnaround times and expert guidance.