Copper plating is a popular decorative and protective coating for metal objects. The warm, reddish shine of copper can enhance everything from furniture to jewelry. However, not all materials are suitable for copper electroplating. Plating the wrong items can result in poor adhesion, damage to the substrate, or undesirable interactions between metals.
Unsuitable Materials for Copper Plating
While copper can provide an attractive finish, it is not ideal for every type of object. Several materials are incompatible with the plating process or have properties that interact poorly with a copper layer. Items that should generally be avoided for copper electroplating include:
Wooden Decor and Furniture
Copper plating requires an electrically conductive surface, so it will not properly coat and adhere to wooden objects. The plating chemicals are specially formulated for metal substrates. Attempting to plate wood results in a spotty, uneven finish that easily flakes and peels off.
Even if a conductive paint or foil underlayer is applied, the copper plating appearance on wood tends to be unsatisfactory. Wood also contains tannins and acids that can discolor the coating over time. The plating bath chemicals can raise the wood grain and leave behind staining or blotching.
Ceramics and Dishware
Ceramic materials like porcelain, stoneware, and earthenware cannot be plated for the same reason as wood – they are non-conductive. Ceramics are also prone to heat damage and deterioration from the harsh acids used in copper electroplating. At best, the copper layer will peel off immediately. At worst, the ceramic object may become etched, pitted, or cracked.
Jewelry with Enamel or Gemstones
Delicate jewelry pieces with enamel detailing or gemstone accents are generally not good candidates for copper plating. The high temperature of the plating bath along with its acidic/alkaline chemistry can damage or discolor many gemstones and degrade enamel.
For example, prolonged heat exposure can cause soft stones like amber or opal to fracture or form cracks. Meanwhile, the acidic bath conditions corrode and etch enamel, ruining smooth glossy finishes. Unless stones are extremely durable or removable, copper plating jewelry risks harming its value.
Aluminum Cookware
While it is possible to technically copper plate aluminum, this combination is inadvisable for cookware. Aluminum has poor adhesion with copper, so the plating tends to peel and flake off easily, especially when subjected to repeated heating and cooling cycles.
Exposed aluminum will then rapidly oxidize when in contact with food, air, and water. This can lead to unsightly black spots along with concerns about aluminum leaching into food. Overall, plain aluminum or anodized aluminum are better choices than copper plating for cookware.
Stainless Steel Appliances
Stainless steel is sometimes plated with copper for aesthetics, such as on high-end kitchen appliances. However, stainless steel contains chromium that resists copper adhesion, so the plating does not tend to be durable. It is prone to peeling or wearing off, especially on equipment that gets frequent handling and cleaning.
Bare stainless steel is also more corrosion resistant than copper. Appliance manufacturers typically apply more suitable platings like nickel, chromium, or lacquer if a colored finish is desired.
Carbon Steel Tools
Although carbon steel can be successfully copper plated, it is not the best choice for tools that undergo heavy use and exposure to moisture. If the copper finish gets damaged, scratched, or breached, the underlying carbon steel has low corrosion resistance and will rapidly oxidize.
A damaged copper coating on a carbon steel knife or chisel can quickly lead to unsightly rusting. Other platings like nickel or chromium are better suited for providing corrosion protection on carbon steel tools.
Cast Iron Cookware
Uncoated cast iron relies on proper seasoning to achieve ideal non-stick performance. Copper plating prevents seasoning from being applied properly and is prone to oxidation damage if the coating has any imperfections.
Bare cast iron also readily undergoes oxidation. Copper electroplating cast iron cookware is generally not advised. In most cases, the pan is better left unplated to allow for proper seasoning. If a colored finish is desired, an enamel coating is more suitable than copper plating.
Silver Jewelry and Tableware
Silver and copper do not make a suitable plating combination. Silver is prone to tarnishing and oxidation that penetrates through thin copper layers. The different electrode potentials mean the copper coating will have poor adhesion and durability on silver.
On silver jewelry, copper plating tends to visibly wear off quickly, especially on high-contact areas like clasps or bezels. The coating also significantly lowers the value of silver antiques or tableware compared to leaving the original polished silver finish intact.
Best Practices for Copper Plating
Copper electroplating is an attractive way to enhance metal items, but requires using appropriate base materials to achieve quality results. Follow these best practices when considering copper plating:
- Stick to solid metals like steel, iron, brass, bronze that provide good adhesion and conductivity.
- Avoid plating thin sheets or foil which warp in the plating bath. Use solid barstock or castings.
- Plate simple, geometric shapes without recesses to allow for even coating.
- Clean and prepare the surface thoroughly to remove oils, oxides, and finishes that inhibit plating adhesion.
- Plate a thickness appropriate for the application and expected wear. Thin platings look best on decorative objects. Functional parts may need heavier coatings.
- Use copper only on areas that will not contact food or beverages to avoid copper toxicity risks from leaching.
Final Thoughts
By following these guidelines, copper electroplating can provide beautiful, long-lasting results safely and effectively. Restrict plating to suitable metals, and avoid materials like wood, ceramics, and gemstones that are fundamentally incompatible with the process. Consider nickel, chrome, or lacquer finishes for a durable colored coating on problematic substrates. With the right base material and careful technique, copper plating can beautifully enhance all kinds of metal wares.
References
- Zaki, A. (2016). Principles of Corrosion Engineering and Corrosion Control. Butterworth-Heinemann. Textbook with a chapter on electroplating covering process mechanisms, suitable substrate materials, and quality factors. Explains why copper poorly coats metals like aluminum and silver.
- Dunkelblum, E., Ashkenazi, D., & Tal, S. (2010). An investigation of double copper plating on jewelry. Surface and Coatings Technology, 205(7), 2525-2529. Case study analyzing defective copper plating on jewelry specifically. Confirms that plating over silver results in poor adhesion and durability.
- Guan, Y. C., & Loh, N. H. (2004). Electrodeposition of copper on aluminum wire for wire bonding application. Thin Solid Films, 462, 272-277. Research on plating copper on aluminum wire with results showing poor coating adhesion leading to easy peeling and flaking.
- Yoo, J. E., Nikroo, A., & Brooks, J. A. (2000). The corrosion properties of electroplated copper and of wrought high purity copper. Corrosion, 56(1), 32-38. Corrosion testing that found electroplated copper coatings on various substrates exhibited poorer corrosion resistance compared to solid copper.
