Scientific, Technical, and Special Purpose Gold Plating
Is gold plating right for your project?
We get a large number of inquires relating to the applicability of gold plating for many different purposes. The gold plating services we provide fall into three general categories. The type of plating process we use depends on the customer's specific requirements. Many times the customer requirements are a combination of the following types of plating.
If you are wondering if gold plating may be right for your needs you may want to refer to the information that follows chronicling clients we serve that have special needs. If you need more information on the properties of different types of gold plate please feel free to e-mail our technical department with your questions. firstname.lastname@example.org
A large number of inquires for gold plating we receive are for decorative purposes. While there are other metals that have the same general appearance as gold, they usually don't offer the same corrosion resistance and combination of physical properties as gold plating.
Gold plating is also very economical as a decorative finish when compared to the other options. This is especially true when you consider that much of the cost of providing a decorative electroplated finish is incurred in the preparation of the surface prior to the final finish. An excellent example of this is in jewelry restoration. The antique copper bracelet we restored. It required hours of tedious labor to prepare the bracelet for plating, this is where most of the cost was incurred. The actual value of the gold we applied was just a few dollars.
However, as far as the owner was concerned it turned a piece of useless jewelry into a valuable heirloom that will be passed on for generations. Generally speaking, the cost of decorative gold plating is ranges from $2.00 - $3.00 per square inch (.25m to .55m thick). This would not include any unusual finishing, restoration, special handling or pretreatment. Of course the price also is dependent on other factors such as quantity, size and special tooling that may be required.
Many people are rightly concerned about the softness of 24K gold for decorative applications. We recognize the limitations of all electrodeposited finishes and strive to give the customer the best information possible for making a choice that is the most suitable for their purposes. There have been many times when we have indicated that gold plating is not appropriate for a particular purpose and have helped the customer decide on a different choice.
For decorative gold applications, we normally recommend a cobalt hardened 24 karat gold. This gold is a 99.7% pure gold, is extremely corrosion resistant, and is about three times as hard as the pure gold we use for medical, electronic and other applications where hardness isn't required and purity of deposit is.
2. Corrosion Resistance
Because of the relative low cost and high resistance to many corrosive environments, we provide a great deal of gold plating that has the primary purpose of providing corrosion resistance to a substrate that otherwise would quickly corrode, such as copper. This need arises quite often because the desirable electrical properties of copper is quickly diminished by the reactive nature of the copper surface. While gold is not as conductive as most copper or silver, gold does provide much better resistance to corrosion than either metal. Hence, we often provide a gold plate over a copper or silver substrate.
An excellent example of using gold plating as a corrosion resistant barrier for a copper substrate is below. The RF load coil shown is a key component of an inductively coupled plasma mass spectrometer, (ICP-MS). These coils operate in an extremely harsh environment under high temperatures, and have to withstand high frequency electrical current without significant degradation of the surface. The scientist who developed, and patented these high performance, corrosion resistant coils had tried different combinations of transition elements before settling on this particular process which involves the application of an extremely heavy pure gold electroplate over a copper substrate with a transition element diffusion barrier.
Even a bright, hard gold plate is somewhat porous; therefore when the gold is applied over a substrate that poses the possibility of diffusing through the gold, such as silver or a copper alloy, we normally suggest a transition element diffusion barrier such as nickel, rhodium or palladium. This will help insure that the substrate is protected against the environment. We provide gold plating services for some high-energy research laboratories that specify the deposit must not be magnetic.
Since most nickel deposits are magnetic to varying degrees this precludes the use of nickel as a diffusion barrier. In this case we usually recommend increasing the thickness of the gold plate to a level that prevents significant diffusion under most conditions, (25m is generally sufficient), or using a platinum group element such as rhodium or palladium. The new MIL-DTL-45204D references gold plating as a chemical agent resistant coating, (CARC).
3. To provide physical properties unique to gold such as reflectivity or conductivity.
We have many research and development labs contact us about gold plating for their projects because of some of the other known properties of gold plating. One such contact was a company developing a medical laser. The gold plating they required was for excellent reflection throughout the electromagnetic spectrum from visible through near-IR (e.g. up to 820nm and specifically 808nm, the most important wavelength for Nd:YAG lasers). They indicated measurements on our plating in excess of 97% reflection throughout this spectrum. Since they were looking for a reflector that works in the 808nm range, gold was the perfect choice for their project. The reflectors were a Type 316 stainless steel, we provided 15m of hardened gold applied directly to the polished stainless steel surface.
We have another client that produces equipment that utilizes a component that operates in such a harsh environment that nothing they had tried would prevent the item from literally burning up in just a few hours. Our technical staff worked with their development engineers to find a solution that utilized a pure nickel substrate followed by a heavy (25m+) pure rhodium plate with 55m of a 999+% gold deposit. The components produced utilizing this very specialized process have preformed for months of extreme, continuous testing.
4. Gold Plating Stainless Steel items with or without a nickel underplate?
We specialize in gold plating onto stainless steel items for a variety of technical and decorative purposes. The question of using a nickel underplate when plating gold onto stainless steel frequently comes up. Here is an opinion letter regarding nickel underplate for stainless steel that was written by one of our technical advisors. Nickel Underplate When Gold Plating Stainless Steel
Because of its inert chemical properties, versatility of application and relatively low cost, electroplating of gold has proven to be the answer to many engineering and technical problems.