Chrome plating has long been a popular way to provide corrosion protection and enhance the appearance of metal surfaces. However, the process can be expensive, especially for small businesses and hobbyists. Thankfully, several alternative coatings and plating methods offer similar benefits at a lower cost.

Why Consider Alternatives to Chrome Plating?

Chrome plating involves electroplating a thin layer of chromium onto a metal substrate to provide a durable, corrosion-resistant finish. The chrome layer is typically 0.2 – 2 μm thick.

The brilliant mirror-like surface of chrome makes it an attractive decorative finish. It also protects against corrosion and wear, so chrome plating is commonly used in automotive, marine, aerospace, medical, and other demanding applications.

However, conventional chrome plating does have some drawbacks:

Expensive equipment – The chrome plating process requires specialized plating tanks, rectifiers, and ancillary equipment. For businesses with low plating volumes, the capital investment can be prohibitive.
Complex process – Achieving high quality chrome platings requires close process control and high operator skill. Parameters like current density, temperature, chemical concentrations, and agitation must be maintained within tight tolerances.
Hazardous chemicals – Hexavalent chromium (Cr6+), the key ingredient in chrome plating chemistry, is toxic and carcinogenic. Proper ventilation, waste treatment, and environmental controls are essential.
Thickness limitations – It is difficult to build up thick chrome platings more than 2-3 μm using conventional plating. Thicker coatings tend to have poor adhesion and be very brittle.

For many purposes, small parts or decorative platings, there are cheaper alternative processes that can provide adequate wear resistance and corrosion protection without the complications of chrome plating:

Nickel Plating

Nickel plating is one of the most widely used alternatives to chrome for enhancing corrosion resistance and surface appearance.

Electroless nickel and electroplated nickel offer similar properties at a lower cost than chrome:

Electroless Nickel Plating

Electroless nickel (EN) plating is an autocatalytic chemical process that deposits a nickel-phosphorus alloy coating with no external power source required.

Benefits of EN vs. chrome plating:

Much simpler process with minimal equipment needed
No electrical power required
Achieves uniform coatings on complex or recessed surfaces
Often lower per-part plating cost

EN coatings provide excellent corrosion resistance due to their low porosity. A medium phosphorus EN coating with 10-11% phosphorus offers the best mix of hardness, wear resistance, and ductility.

Typical EN layer thickness ranges from 0.005-0.02” (13-51 μm). The coatings are much thicker than chrome for better wear life.

Applications for electroless nickel in lieu of chrome include:

Aerospace hydraulic pistons and landing gear
Food/beverage valve stems and pump shafts
Medical implants and surgical tools
Automotive parts like bumpers and wheels

Electroplated Nickel

Electroplated nickel coatings involve electrodeposition of nickel using an electrical current in a nickel plating bath.

Like chrome plating, specialized plating tanks and rectifiers are needed, but the process is generally simpler and more forgiving than chroming.

Key advantages of electroplated nickel vs. chrome:

Lower capital investment for small plating shops
Less demanding to achieve high quality deposits
No hexavalent chromium chemicals
Can plate thicker coatings up to 0.002-0.012” (50-300 μm)

Electroless nickel undercoats are commonly used prior to electroplated nickel top coats on steel or zinc die cast substrates. The EN provides corrosion protection while the electroplated nickel imparts wear resistance and a bright finish.

Nickel-Tungsten and Nickel-Silicon Carbide

To improve the wear resistance of electroplated nickel, tungsten or silicon carbide particles can be codeposited within the nickel matrix to form a composite coating.

These composite nickel platings offer hardness and abrasion resistance comparable to hard chrome for applications like hydraulic rods, pump shafts, and piston rings.

Key benefits as alternatives to hard chrome:

Lower cost deposition compared to chrome
No hexavalent chromium
Less porous and more uniform coatings
Often superior wear resistance

Thermal Spray Coatings

Thermal spraying involves heating and accelerating fine metal or ceramic powders toward substrates to form protective coatings. Techniques like high velocity oxy-fuel (HVOF) spraying provide excellent alternatives to chrome plating.

Common thermal spray coating materials include:

Nickel and nickel alloys
Stainless steel alloys
Tungsten carbide
Chromium carbide

These materials are sprayed in molten or semi-molten form onto substrates. The deposited coatings are thicker (0.003-0.025”/75-625 μm) than electroplated coats.

Key advantages of thermal spraying vs. chrome plating:

Cost effective for large components or low volumes
Minimal surface prep needed
Can coat external surfaces not reachable with plating
Excellent wear life due to coating thickness

Applications suited to HVOF and other thermal spray chrome alternatives include:

Hydraulic rams and cylinders
Large pump shafts
Rollers
Engine blocks

Physical Vapor Deposition (PVD)

Physical vapor deposition (PVD) uses vaporized metals that condense onto substrates to form thin, hard coatings 0.5-5 μm thick. The process takes place in a vacuum chamber and offers an eco-friendly alternative to chrome plating small parts.

Common PVD coating materials include:

Titanium nitride (TiN) – gold colored, offers wear resistance and corrosion protection
Zirconium nitride (ZrN) – gray finish, low friction
Chromium nitride (CrN) – silvery color, improves corrosion and abrasion resistance

Benefits of PVD vs. chrome plating:

Environmentally friendly process with no water use or discharge
Coats small parts and intricate geometries
Provides excellent abrasion resistance
Decorative metallic or colored finishes

PVD chrome is ideal for small precision parts like:

Cutting tools
Injection molds
Medical instruments
Engine components

Other Chrome Plating Alternatives

Beyond the major coating types covered already, there are a few other processes that can serve as lower cost substitutes for chrome plating in specific applications:

Anodizing

Anodizing creates a protective aluminum oxide coating on aluminum alloy parts. It offers an alternative to chrome for improving corrosion resistance and surface hardness. Anodizing penetrates deeper into the substrate than chrome platings. Common for architectural applications.

Powder Coating

Powder coating is an economical protective finish for automotive trim pieces, bike/auto parts, and metal furniture. The powdered polymer coating is applied electrostatically then cured under heat. Provides color and corrosion resistance.

Plasma Nitriding

Plasma nitriding thermochemically infuses nitrogen into steel’s surface to create a hard, wear-resistant case. It can provide similar benefits to hard chrome plating on parts like automotive valves and bearings.

Titanium Nitride (TiN) Coating

TiN applied by PVD provides an attractive gold colored coating. It is commonly used in lieu of chrome plating on automotive trim pieces and bathroom faucets. Offers good corrosion resistance and hardness.

When to Choose Alternatives Over Chrome Plating

Consider substituting an alternative coating process for chrome plating in these situations:

For small production runs when chrome line setup costs are prohibitive
To avoid chrome plating safety hazards and waste treatment
If part geometries are complex or have blind holes/recesses
When very thick coatings over 25 μm are needed for wear resistance
For coating non-conductive substrates like plastics or ceramics
If a colored finish other than chrome is desired

However, conventional chrome plating still offers the best corrosion protection for demanding applications like marine components. It also provides the most lustrous and reflective decorative finish.

Conclusion

Chrome plating has been a trusted and versatile metal finishing technique for over 80 years, but it comes with significant costs and environmental considerations.

Fortunately, modern coating technologies like PVD, thermal spraying, and electroless nickel provide quality, lower-cost alternatives for many applications that traditionally used chrome plating.

Each chrome alternative has its own set of benefits and limitations depending on the substrate, service environment, and desired part properties. By matching the coating method to the application, excellent results can be achieved while avoiding the complications of conventional chrome plating.

References

Gu, Jincheng, et al. “Replacement of Electroplating Chromium for Hydraulic Piston Rods by Thermal Spraying Coatings.” Coatings, vol. 8, no. 11, p. 379, 2018. https://doi.org/10.3390/coatings8110379
Mallory, Glenn O., and Juan B. Hajdu. Electroless Plating: Fundamentals and Applications. William Andrew, 1990.
“Chrome Plating Alternatives.” Sharretts Plating Company, https://www.sharrettsplating.com/chrome-plating-alternatives/.
Chromizing Versus Chrome Plating: Which is Better? Curtiss-Wright Surface Technologies, 2013, https://cwst.com/wp-content/uploads/2019/12/chromizing_versus_chrome_plating.pdf.
Chrome Plating. The Corrosion Doctors, https://www.corrosion-doctors.org/Electroplating/Chrome-plating.htm.