Precious Metals Plating
GOLD
MIL-G-45204
MIL-DTL-45204
ASTM B-488
SILVER
QQ-S-365
ASTM B700
RHODIUM
MIL-R-46085
Our precious metal capabilities include seven different gold options, 12 types of silver and two special rhodium platings.
Gold will be yellow to orange in color depending on the proprietary process used. It will range from matte to bright finish depending on the base metal. It exhibits good corrosion resistance, good conductivity, high tarnish resistance, and excellent solderability.
Silver plating can be white matte to very bright in appearance and depending on the base metal will have good corrosion resistance. Although it will tarnish easily silver is one of the better electrical conductors. Solderability is excellent but does decrease over time. Certain types of silver perform very well on seals, bushings and high friction applications because of its excellent lubricity and smear characteristics.
Rhodium is the rarest of the precious metals offered and is similar to stainless steel in color. Its metallic appearance lends to its high reflectivity, and thicker coatings are very brittle. Rhodium is almost as hard as chromium, has good abrasion resistance and excellent corrosion resistance. In fact, once plated the best methods for removal are mechanical. Very few acids are strong enough to break down this coating.
Plating Characteristics
Conductivity
Solderability
Wear Resistance
Reflectivity
Corrosion Resistance
High Tarnish Resistance
Low Emissivity
Low Contact Resistance
Typical Lead Times
Can be same day but typically 3 to 5 days
Quoted on job by job basis
Gold Plating Properties
Gold plating performs well as a reflector for infrared radiation. In addition to being a precious metal, gold is also a noble metal that does not oxidize or chemically react under normal conditions. We frequently see gold plating as a preference where electrical conductivity, solderability and corrosion resistance are desired.
The appearance of gold plating is very much a function of the underplate that is applied prior to deposition of the final gold layer. The most common underplate for gold plating is nickel. If a matte nickel like sulfamate nickel is applied, the final gold deposit will have more of a matte appearance. If a bright nickel such as bright electroless nickel is utilized, the gold plating will have a bright appearance. As with any plating, the surface finish/condition of the base metal is the most important factor in the final appearance of the gold plating.
Alexandria Metal Finishers offers gold plating from 99.0% to 99.9% purity. The two most common gold plating specifications certified by Alexandria Metal Finishers are MIL-G-45204 and ASTM B488.
Silver Plating Properties
Silver is a ductile metal and is naturally off-white in appearance when plated. We have mastered the ability to manipulate our plating baths so the appearance of the silver plating can range from matte to bright. Matte silver plating is less brittle and solders better than bright silver. It has the highest electrical and thermal conductivity of all metals as well as the highest optical reflectivity in the visible range. Unlike copper, oxidized silver retains its conductive surface.
Silver is harmful to a number of micro-organisms and has found use in many medical applications. In fact many filtration systems often utilize this property of silver to fight the growth and transmission of harmful organisms.
Silver has found extensive use in the telecom industry. Silver will tarnish if not stored and packaged properly. Silver tarnish is not an oxide and silver oxide does not form easily. Silver oxide is electrically conductive and has a low contact resistance. For these reasons, silver plated conductors have many advantages over other plating materials and we are very versed in the handling of silver plated parts.
Alexandria Metal Finishers offers silver plating with up to 99.9% purity. The two most common silver plating specifications certified by Alexandria Metal Finishers are QQ-S-365 and ASTM B700.
Rhodium Plating Properties
Rhodium is white in color, has a high melting point, is very dense, very hard, and exceptionally resistant to corrosion. Rhodium is the hardest of the precious metals we offer at Alexandria Metal Finishers with a knop hardness of around 800. Rhodium is an excellent choice where contact with corrosive gases or other high corrosion environments will be encountered, as such we see it often used for critical applications. As the operating temperature increases, the corrosion resistance will also increase. So in high temperature applications, rhodium will provide a longer life cycle than, for example, gold will. Also, because of its high temperature tolerance to oxidation, rhodium is an extremely good choice for electrical contacts where contact arcing would otherwise cause the formation of electrically resistive oxide formations on the contact surface.
Alexandria Metal Finishers offers rhodium plating for many different applications. The most common rhodium plating specification certified by Alexandria Metal Finishers is MIL-R-46085.