What is Electroplating?
Electroplating often raises tough design questions: Will it change my tolerances? Improve corrosion resistance? Add lead time? Engineers and product developers need clear answers before committing plating to a part specification. This post is written to resolve those doubts with practical, data-backed guidance.
Electroplating applies a thin, controlled layer of metal onto a base material using electrical current. It is primarily used to improve corrosion resistance, surface durability, conductivity, or appearance. Designers must account for its impact on dimensional accuracy, cost, and process flow during manufacturing.
Learn which materials can be plated, how coatings impact fit and function, and the risks that lead to defects—so you can design and source with confidence.
Table of Contents
What does electroplating change in my design?
Electroplating isn’t just cosmetic — it modifies your part geometry and surface in ways that affect function. A typical plating layer of 5–25 µm changes effective dimensions, alters surface finish, and may introduce inspection requirements you’ll need to call out clearly in your drawings.
The most common issue is dimensional buildup. Even a thin layer can shift fits if your design relies on tight tolerances. For example, clearance holes may shrink, or threads may bind after plating. That’s why it’s essential to specify whether tolerances apply before plating or after plating. Without this note, suppliers may interpret it differently, leading to mismatches or costly rework.
Surface finish is also impacted. A rough-machined Ra 3.2 µm surface may smooth closer to Ra 0.8 µm after plating, improving sealing or aesthetics. On the other hand, poor base prep can cause pits or nodules that reduce performance instead of improving it.
Design Takeaway: Treat plating as a functional part of your design, not an afterthought. Always include plating thickness in your specification, and state clearly on drawings whether tolerances apply pre- or post-plating to avoid assembly problems or inspection disputes.
When should I consider electroplating for my parts?
Electroplating is worth specifying when your part requires corrosion resistance, added wear life, improved conductivity, or a specific surface appearance that machining alone can’t achieve. If your design faces demanding environments or customer-facing aesthetics, plating should be considered from the CAD stage.
For corrosion: zinc and nickel plating are typically specified once exposure exceeds 48–96 hours in salt spray tests or involves continuous high humidity. In medical and consumer devices, plating is recommended where the part has direct skin contact to avoid irritation or tarnishing. For wear applications, hard chrome or nickel plating extends surface life when contact cycles are high or lubrication is unreliable.
On the other hand, purely structural parts with large clearances or protected internal use may not justify the cost or lead time of plating. Typical plating adds 2–5 days of processing time and introduces another vendor stage, which can delay delivery if not planned early.
Design Takeaway: Specify electroplating when your part faces corrosion, wear, or electrical requirements, or when surface appearance is part of product value. If plating is likely, note it in the CAD and RFQ stage to avoid late design changes or sourcing delays.
Which base materials can be electroplated successfully?
The most reliable plating bases are copper, brass, steel, aluminum, and zinc alloys. Each material responds differently, and some require special pretreatments. Plastics and composites can also be plated but are less predictable for critical features.
- Copper / Brass → Excellent adhesion, ideal for conductive and decorative finishes.
- Steel → Common and versatile; accepts nickel, chrome, and zinc plating well for corrosion and wear resistance.
- Aluminum → Plateable but requires a zincate or strike layer for adhesion; not all plating shops handle this reliably.
- Zinc alloys → Often plated for added corrosion resistance in cost-sensitive applications.
- Stainless steels → Usually not plated due to inherent corrosion resistance; adhesion can be inconsistent.
- Plastics / composites → Possible with chemical pretreatments, but variation is high and generally avoided in precision assemblies.
Base Material Plating Reliability Common Notes
Copper / Brass ★★★★★ (Very high) Strong adhesion, excellent for conductivity & appearance
Steel ★★★★☆ (High) Versatile, standard plating practice
Aluminum ★★★☆☆ (Moderate) Needs zincate layer; not every shop offers
Zinc alloys ★★★☆☆ (Moderate) Good for corrosion resistance at low cost
Stainless steel ★★☆☆☆ (Low) Rarely plated; adhesion inconsistent
Plastics ★☆☆☆☆ (Very low) Only for non-critical or cosmetic use
Design Takeaway: Prioritize copper, brass, steel, or aluminum for electroplated designs. If using aluminum, confirm your supplier can handle the adhesion layer. Avoid relying on plating for critical tolerance parts when working with stainless steels, plastics, or composites.
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What metals are most commonly used for electroplating?
The most widely used plating metals are nickel, zinc, chrome, gold, silver, and tin. Each is chosen for a specific functional or aesthetic purpose, and selecting the right one depends on whether your part needs corrosion resistance, wear life, conductivity, or appearance.
- Nickel → General-purpose plating for corrosion and moderate wear; often used as a base layer under chrome or gold.
- Zinc → Low-cost corrosion protection for steel, common in automotive and industrial parts.
- Chrome (hard or decorative) → Hard chrome improves wear life; decorative chrome provides a bright finish.
- Gold → Excellent conductivity and corrosion resistance, but very expensive; used for contacts in electronics or medical connectors.
- Silver → High conductivity and antimicrobial properties; often specified in RF or medical applications.
- Tin → Popular in electronics for solderability and light corrosion protection.
⚠️ Watch-out: plating is not interchangeable. We’ve seen designs call for chrome when the part only needed zinc for corrosion resistance — that mistake multiplied cost with no benefit.
Design Takeaway: Select plating metal based on function, not just looks. Nickel or zinc suit general corrosion resistance, chrome fits wear surfaces, and gold/silver are reserved for critical conductivity. If you’re unsure, confirm the requirement early rather than relying on the finisher to “pick one.”
How does electroplating affect part tolerances and fit?
Electroplating adds thickness in the range of 5–25 µm per surface, which can significantly alter tight clearances, bores, and threaded features. If tolerances are not adjusted or called out as “after plating,” the part may fail assembly even if the machining was correct.
Take a bore designed at 10.00 mm ±0.02 mm. After 10 µm plating on each wall, the effective bore drops to 9.98 mm — instantly out of spec. Threads are another frequent issue: we’ve seen entire production runs scrapped because designers forgot to oversize before plating, leaving fasteners seized.
Surface finish can improve (Ra 3.2 µm reduced to ~0.8–1.6 µm with nickel) or worsen if the base prep wasn’t good — plating won’t hide machining marks; it can actually highlight them. Dimensional changes are rarely uniform, so critical fits should always be inspected after plating, not assumed.
⚠️ Don’t assume ISO 2768 tolerances account for plating — they don’t. Standards like ASTM B456 (nickel) or ASTM B633 (zinc) define thickness and inspection requirements, but it’s up to the designer to show if dimensions apply pre- or post-plating.
Design Takeaway: Always build plating thickness into your CAD. Oversize threaded or clearance features where needed, specify before/after plating on drawings, and mark which dimensions must be verified after finishing. Skipping this step is a common — and expensive — oversight.
Does electroplating improve corrosion resistance and wear life?
Yes, but how much it helps depends entirely on the plating metal and thickness you specify.
- Corrosion protection: Zinc and nickel are the go-to choices. Zinc-plated steel can withstand hundreds of hours in salt spray before red rust appears, making it a cost-effective solution for industrial or automotive use. Nickel, especially when layered, offers stronger resistance and is often used in consumer and medical housings where appearance and longevity both matter.
- Wear life: Hard chrome and electroless nickel add surface hardness. A thin layer of hard chrome can dramatically extend the service life of sliding shafts or tooling, provided the base material is stable.
⚠️ Important: plating is not a magic shield. Thin layers wear through quickly if the part is under continuous abrasion. If your design truly relies on long wear cycles, pair plating with a proper base material (e.g., hardened steel) rather than treating plating as the sole line of defense.
Decision point: Use plating for corrosion and moderate wear protection, but don’t rely on it alone in high-load applications. Always specify thickness, not just “plated finish,” if corrosion and wear life are critical to your product’s function.
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Can electroplating improve electrical conductivity?
Yes, but only certain plating metals improve conductivity — and only when applied correctly.
- Gold → Excellent conductivity and corrosion resistance, stable over time; common for electronic connectors.
- Silver → Even more conductive than gold, but tarnishes quickly in air unless sealed; often used in RF or high-frequency applications.
- Tin → Cost-effective for solderability and decent conductivity, but not as durable.
⚠️ A common design mistake is assuming “any plating = better conductivity.” Nickel, for example, is widely used for corrosion resistance but actually lowers conductivity compared to copper. If your part’s function depends on electrical performance, plating choice matters as much as thickness.
Decision point: Specify gold or silver plating only where consistent conductivity is critical (e.g., signal connectors, sensor pads). For general-purpose housings or mechanical parts, conductivity gains are negligible and don’t justify the cost. Always confirm whether conductivity requirements apply across the entire part or only on localized features.
What surface preparation is required before electroplating?
Electroplating only works if the base surface is clean, smooth, and free from oxides. Oils, machining marks, or burrs will directly carry through the plating layer. Standard prep includes cleaning, degreasing, and acid etching. For aluminum, a zincate strike layer is required to ensure adhesion.
The material removal from etching is usually just a few microns, but on thin-walled parts or tight-tolerance bores this can be enough to matter. Designers should consider this when specifying minimum wall thickness.
Some features almost always need masking before plating:
- Threaded holes → prevent buildup that seizes fasteners
- Bearing bores → avoid tolerance changes that block assembly
- Sealing faces → keep plating out of gasket zones
⚠️ Don’t assume plating will hide flaws. In reality, it highlights them. We’ve seen parts rejected because a Ra 6.3 µm surface was plated without refinement, and the final finish looked worse.
Decision point: Define required base Ra finish in drawings and call out which features must be masked or pretreated. This avoids disputes later and keeps plating from creating new assembly or cosmetic problems.
What plating defects or risks should I watch for?
The most common plating defects are uneven thickness buildup, pitting, peeling, and hydrogen embrittlement in high-strength steels. These risks affect tolerance control, surface reliability, and fatigue strength. Most can be prevented with clear design notes — such as specifying thickness, masking critical features, and requiring post-plating inspection.
Defect Likelihood Impact Design Control
Uneven thickness buildup Common Tolerance failures on edges/bores Specify thickness tolerance; flag critical features
Pitting / nodules Common Poor sealing or cosmetic rejection Define Ra before plating; supplier manages prep
Peeling / blistering Moderate Early corrosion or total finish failure Confirm base material & adhesion layer (zincate for aluminum)
Hydrogen embrittlement Rare but critical Catastrophic fatigue failure in steels >1000 MPa Require post-bake after plating
We’ve seen batches scrapped because plating thickness was left undefined — suppliers guessed, and critical fits failed. Another frequent trap is unmasked threads, which lock fasteners after plating and force costly rework.
Decision point: Specify thickness in microns, call out features that must be masked, and require post-plating inspection on critical dimensions. For high-strength steels, always add a post-bake note to prevent embrittlement failures.
Does electroplating add extra lead time to production?
Yes — electroplating typically adds 2–5 working days, but timing depends heavily on the metal, layer thickness, and order size. Zinc or nickel coatings can often be completed within a few days, while gold, silver, or hard chrome may extend timelines by a week or more, especially if certification paperwork is required.
Most plating is subcontracted, meaning parts leave the machine shop, travel to a finishing house, and then return for inspection. Each handoff introduces scheduling risk. For prototypes, delays are more common — many platers run in batch cycles, so a single part may wait until a batch is ready to process.
We’ve seen schedules slip when plating was requested after machining started, or when the RFQ didn’t include plating at all. These oversights lead to disputes once extra days are added later.
Decision point: As a rule of thumb, always budget up to a full week of extra lead time if plating is critical to your design. Note plating in your RFQ, confirm supplier capacity, and ask specifically how prototypes are handled. If deadlines are tight, consider alternative finishes like anodizing for aluminum, which may be faster.
Conclusion
Electroplating can enhance corrosion resistance, wear life, and conductivity — but only if design details like tolerances, masking, and lead time are addressed early. Contact us to explore manufacturing solutions tailored to your electroplated component requirements, ensuring performance without costly surprises.
Frequently asked questions
State the required thickness in microns (e.g., “Nickel plate 10–15 µm”) and whether dimensions apply before or after plating. For critical features, add an inspection note requiring verification post-plating.
At minimum: thickness verification (XRF or cross-section test). For aerospace or medical, expect adhesion testing, salt spray results, or certificates per ASTM/ISO standards. Request these at RFQ stage so suppliers price in the compliance work.
In prototyping, platers may not run small lots immediately — lead times are less predictable. For production, plating is scheduled in batch cycles with more consistent turnaround. Always flag plating early in prototypes to avoid delays.
Usually not if the pad itself is the plated feature (e.g., gold contacts). But if the base conductivity must remain bare, explicitly call out masking. Unmasked pads can lose function if covered with non-conductive metals like nickel.
For general corrosion resistance, zinc plating as thin as 5 µm provides short-term protection. For functional parts, 8–12 µm is typical, while hard chrome often exceeds 20 µm. Anything thinner risks uneven coverage or premature wear.
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Yes, but sequence matters. Anodizing is only for aluminum and generally not combined with plating. Powder coating can follow plating for added protection, but tolerance changes stack up quickly — confirm with your finisher before combining.
