Graphite and Precious Metals
Graphite plays an essential role in the processing of precious metals, particularly in refining, alloying, and purification processes. Although creating graphite molds for gold ingots or jewelry production doesn’t make up the bulk of our business at Semco, we do think the components we machine for the precious metal industry are pretty cool and exciting. Let’s start by going over some ways graphite is used in the processing of precious metals.
Graphite Molds and Graphite Crucibles
Graphite molds and graphite crucibles are widely used in the melting and casting of precious metals. Graphite's high melting point and excellent thermal conductivity make it an ideal material for containing and transferring heat during the melting process. Graphite's resistance to thermal shock makes it suitable for containing molten metals during processes such as smelting, alloying, and refining. Graphite crucibles are commonly used for melting gold, silver, platinum, and other precious metals so that they may be shaped (using graphite molds) into ingots or other more refined forms. Since the standards for gold and silver ingots set by the London Bullion Market Association are so exacting, the ingots need to be made of the right material and need to be machined by experts like our graphite machining technicians at Semco.
Graphite Anodes in Electroplating
Electroplating is a process that involves depositing a layer of precious metal onto a base material. Graphite anodes are often used in electroplating baths, where they provide a source of metal ions for deposition onto the target material. For example, in gold plating, a graphite anode can be used to dissolve gold ions into the electrolyte.
Electrodes in Electrolytic Refining
Electrolytic refining is a common method used to purify precious metals. In this process, graphite electrodes serve as conductive materials through which electric current passes. These electrodes help to separate impurities from the precious metal being refined, enabling purification. In electrorefining, graphite anodes are used to oxidize impurities from the anode material, while a cathode made of a precious metal attracts and collects the pure metal ions. If you’ve ever dealt in precious metals, or just bought a wedding ring, you know how important purity is in this industry. Graphite helps make that purity a reality.
Graphite Crucibles for Fluxing and Assaying
But speaking of purity, how is a consumer or producer to know whether or not a block of precious metal is pure? In assaying precious metals (determining their composition and purity), graphite crucibles are commonly used for fluxing. Fluxing refers to the addition of certain chemicals or agents to aid in the separation of impurities from the precious metal. The graphite crucible provides a suitable container for this process because graphite has low chemical reactivity. It is unlikely that in this purification process the graphite will contribute any impurity by reacting with the chemicals used in fluxing.
Graphite Molds for Jewelry Production
Graphite molds are used in jewelry manufacturing to create precise and intricate shapes for precious metal casting. High-density graphite grades can be cut and shaped into these intricate designs, and the high thermal conductivity of graphite allows for efficient heat transfer during the solidification process, ensuring accurate reproduction of the mold's design. In addition, graphite has a low coefficient of friction, and is often used as a dry lubricant. What that means for graphite molds used in jewelry production is that the precious metal pieces slide right out of the graphite molds and don’t degrade or become damaged by sticking to the sides. Graphite also does not directly interact with the precious metals themselves. Graphite's properties make it a valuable tool in facilitating the processing and refining of precious metals, contributing to their high-quality and purity.
Stirring Rods and Stirrers
Graphite stirring rods or stirrers are used in molten metal processes like alloying to facilitate mixing and homogenization of alloys. They can withstand the high temperatures and corrosive nature of molten metals, allowing for efficient blending of different metals and ensuring uniform composition.
How to Make Your Precious Metal Project a Reality
Graphite's excellent thermal and electrical conductivity, high-temperature resistance, and chemical stability make it a valuable material in various stages of precious metals processing, from melting and refining to shaping and alloying. If you want to create a special silver ingot or a unique silver ring, or if you want to shape a precious metal in any other way, consult our graphite machining experts at Semco. We can work with you to create custom graphite components for your precious metal project.