- Cadmium–zinc alloys are metallic materials formed by combining cadmium and zinc in varying proportions, resulting in a solid solution or multiphase mixture with properties intermediate between those of the two constituent metals.
- Both cadmium and zinc are relatively soft, low-melting, corrosion-resistant metals with hexagonal close-packed crystal structures, and they exhibit complete mutual solubility in the liquid state. In the solid state, however, their solubility is limited, leading to the formation of distinct microstructures that can be tailored by controlling composition and cooling rate.
- The alloys generally appear silvery-white with a bluish tinge, are malleable, and retain the relatively low melting points characteristic of both metals.
- Structurally, cadmium–zinc alloys may consist of a primary solid solution phase where zinc atoms substitute into the cadmium lattice (or vice versa), along with secondary intermetallic or segregated phases at grain boundaries depending on composition. Because cadmium has a slightly larger atomic radius and higher density than zinc, increasing cadmium content tends to produce heavier, softer alloys with improved resistance to atmospheric corrosion but reduced mechanical strength. Conversely, zinc-rich cadmium alloys tend to be harder, stronger, and more wear-resistant, though they may sacrifice some corrosion performance in marine or acidic environments. The alloys are also good conductors of electricity, and their electrical resistivity varies smoothly with composition, making them suitable for specialized electrical components.
- The preparation of cadmium–zinc alloys typically involves melting high-purity cadmium and zinc metals together under an inert atmosphere or in a reducing environment to prevent oxidation, followed by casting into ingots, sheets, or wires. Alloying can also be achieved through electrochemical codeposition from aqueous or molten salt electrolytes, which allows thin films or coatings of cadmium–zinc to be produced directly on substrates. The precise cadmium-to-zinc ratio is chosen to achieve the desired balance of properties, with typical compositions ranging from a few percent cadmium in zinc (for plating applications) to nearly equal proportions in certain corrosion-resistant solders.
- Industrial uses of cadmium–zinc alloys have historically centered on protective coatings and corrosion-resistant platings, particularly for fasteners, aircraft components, and marine hardware. The addition of cadmium to zinc coatings improves resistance to saltwater corrosion and offers better lubrication properties, making the coatings valuable in aerospace and defense industries. In electronics, cadmium–zinc alloys have been used in connectors, contacts, and fusible links, where their low melting points and stable electrical properties are advantageous. Certain high-cadmium alloys have also been employed in low-pressure casting and as bearing materials due to their good wear resistance and anti-galling characteristics.
- From a safety and environmental perspective, cadmium–zinc alloys are hazardous because of their cadmium content. Cadmium is highly toxic, carcinogenic, and bioaccumulative, posing serious risks to human health and the environment through inhalation of fumes, ingestion of dust, or long-term exposure to leachates from discarded materials. As a result, many countries have heavily restricted or phased out the use of cadmium-containing alloys in consumer products, replacing them with safer alternatives. Where they are still permitted, strict handling protocols, fume extraction during melting or machining, and secure recycling systems are essential to minimize health risks and environmental contamination.
