Zinc Plating Service
Resolute Precision Manufacturing coordinates zinc plating for precision CNC machined steel components requiring corrosion protection beyond what black oxide provides. Electrodeposited zinc provides both barrier protection and sacrificial anodic protection, helping protect steel components from corrosion even when the coating is scratched or damaged.We deliver zinc-plated components with available chromate conversion coatings and required certification through a single purchase order. For manufacturers searching for zinc CNC machining services and precision zinc parts, our team can coordinate machining and zinc plating requirements based on the component material, dimensions, application, and finish requirements. Request a QuoteHow Zinc Plating Protects Steel
Zinc plating provides corrosion protection through two mechanisms.
Zinc plating protects steel components through two mechanisms.
First, the zinc deposit creates a physical barrier between the steel substrate and the surrounding environment, helping prevent moisture and oxygen from reaching the steel surface.
Second, zinc provides sacrificial anodic protection. Zinc is more electrochemically active than steel, so when both metals are exposed to a corrosive environment, the zinc corrodes preferentially. This sacrificial action helps protect the underlying steel.
As a result, zinc-plated steel components can continue receiving protection around scratches, cut edges, and other areas where the underlying steel may become exposed.
Zinc plating is widely used for precision machined steel components where corrosion resistance, controlled coating thickness, and dimensional considerations are important.
Our Services
Chromate Conversion Coating on Zinc
Zinc plating is commonly followed by a chromate conversion coating to improve the corrosion resistance of the zinc surface and provide the specified appearance.
Common options include:
Clear chromate — A thin conversion coating with a bright or silver metallic appearance and standard corrosion protection.
Yellow/iridescent chromate — An iridescent yellow or amber appearance with enhanced corrosion protection compared with some clear finishes.
Black chromate — A black conversion finish used when a dark appearance is required along with corrosion protection.
Trivalent chromate (Cr³⁺) options are available where required for environmental and regulatory requirements.
Specifications
| Standard | ASTM B633 SC1/SC2/SC3/SC4, MIL-PRF-27418, and customer specifications |
| Deposit Thickness | SC1: 0.0001″ (light service); SC2: 0.0002″ (mild service); SC3: 0.0003″ (moderate service); SC4: 0.0005″ (severe service) |
| Chromate Finish | Clear (Type II), yellow iridescent (Type III), and black (Type IV) |
| Salt Spray Performance | SC1 clear: 12 hours; SC2 yellow: 96 hours; SC3 yellow: 120 hours; SC4 yellow: 200 hours (typical) |
| Dimensional Impact | 0.0002″–0.0005″ per side, depending on the specification; should be considered for threaded and mating features |
| Materials | Carbon steel and alloy steel; not recommended for stainless steel, aluminum, or copper alloys |
| RoHS Compliance | Trivalent chromate (Cr3+) available; compliant with RoHS and ELV directives |
| Documentation | Plating certification, coating thickness reports, and salt spray test data provided with finished parts |
| ISO | ISO 9001:2015; outside suppliers qualified under RPM’s approved vendor procedures |
Zinc Plating Applications
Zinc plating is commonly specified for steel machined components used in applications where corrosion protection and controlled coating thickness are important.
Fasteners — Zinc-plated machine screws, bolts, nuts, and other steel hardware for industrial applications.
Hydraulic and pneumatic components — Corrosion protection for steel fittings and components exposed to moisture and wet environments.
Automotive components — Zinc-plated steel components manufactured to applicable OEM or customer specifications.
Industrial machinery hardware — Brackets, fittings, shafts, and other machined steel components used in outdoor or washdown environments.
Agricultural and construction equipment — Steel components exposed to humidity, moisture, and demanding operating environments.
Precision Zinc Parts and CNC Machining
When zinc plating is specified for a CNC machined component, coating thickness needs to be considered during part design and manufacturing. Threads, bores, mating surfaces, and other close-tolerance features may require specific allowances to accommodate the plating thickness.
Resolute Precision Manufacturing can coordinate machining and finishing requirements for precision zinc parts, helping ensure that the finished component meets the applicable dimensional and coating specifications.
For projects requiring zinc CNC machining services, contact our team with your drawing, material specification, quantity, tolerance requirements, and desired finish. We can review the requirements and coordinate the appropriate machining and zinc plating process.
Frequently Asked Questions
What is the difference between zinc plating and hot-dip galvanizing?
Electrodeposited zinc plating produces a thin, uniform, precise coating (0.0002″–0.0005″) suitable for precision machined components. Hot-dip galvanizing applies a much thicker coating (0.003″–0.005″) by immersion in molten zinc appropriate for structural steel and fabrications but not for threaded or precision-fit components.
Does zinc plating affect the dimensions of threaded parts?
Yes. Zinc plating builds 0.0002″ to 0.0005″ per surface. On external threads, this reduces the thread clearance. Common practice is to plate external threads before final inspection and internal threads after plating. We advise on the appropriate threading and plating sequence during quoting.
Is hex chromate (yellow zinc) RoHS compliant?
Traditional hexavalent chromate (Cr6+) is not RoHS compliant. Trivalent chromate (Cr3+) is available and provides comparable corrosion performance while meeting RoHS and ELV directive requirements. We specify trivalent chromate for all RoHS-sensitive programs unless hexavalent is specifically required
What corrosion resistance does yellow zinc provide?
Yellow zinc chromate (SC2 or SC3 per ASTM B633) typically provides 96 to 200 hours to white rust in salt spray testing per ASTM B117. This is appropriate for moderate industrial environments. For severe or marine environments, electroless nickel or zinc-nickel alloy plating provides substantially better performance.