The effects of Cadmium (Cd) and Tellurium (Te) on steel
Cadmium and tellurium both have significant effects on steel properties. Cadmium can enhance corrosion resistance but poses risks of brittleness and toxicity, while tellurium can lead to embrittlement and affect magnetic properties.
Cadmium (Cd) in Steel
Cadmium (Cd) is a Group II B element with atomic number 48 and atomic mass 112.4. It is a soft, ductile metal with a silvery-white or lead-gray appearance. Cd has a density of 8.642 g/cm³, a melting point of 320.9°C, and a boiling point of 765°C. While cadmium is known for its industrial uses, such as electroplating, cadmium compounds are toxic and are closely monitored in environmental protection programs.

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One of the significant applications of cadmium in the steel industry is its use as a protective coating on steel surfaces. Cadmium plating provides corrosion resistance, making it a valuable coating material, especially in environments where steel is exposed to harsh conditions. However, outside of this specific application, cadmium is generally considered a harmful element in steel alloys.
The primary reason for cadmium’s negative reputation in steel is its adverse impact on mechanical properties. High concentrations of cadmium can cause cadmium brittleness, leading to a severe reduction in the toughness and overall durability of steel. This makes cadmium a hazardous trace element that must be carefully controlled, especially in structural applications where mechanical integrity is crucial.
Tellurium (Te) in Steel
Tellurium (Te), a Group VI A element, has atomic number 52 and atomic mass 127.60. Te exists in two allotropic forms: crystalline tellurium, which has a silvery-white metallic appearance, and amorphous tellurium, which is brown in color. The density of crystalline tellurium is 6.25 g/cm³, with a melting point of 452°C and a boiling point of 1390°C. Amorphous tellurium has a slightly lower density of 6 g/cm³ and a melting point of 449.5°C. Tellurium is considered an important material in high-tech fields, including aerospace, military, medicine, metallurgy, and electronics.
In steelmaking, tellurium is often regarded as an undesirable trace element. Similar to sulfur (S), Te can adversely affect the magnetic properties of low-carbon or soft steel if present in significant amounts. More critically, tellurium is known to cause intergranular embrittlement, which can significantly reduce the long-term strength and plasticity of steel. This makes Te a harmful element in steel alloys unless specifically introduced for a particular purpose.
Tellurium’s embrittling effect is particularly detrimental in high-temperature alloys used in aerospace applications, where strength and resistance to stress are vital. Therefore, stringent controls are imposed on tellurium content in these materials, typically limiting the amount of Te to less than 0.001%. In some high-performance applications, the Te content is restricted to as low as 1–0.5 ppm to avoid compromising the steel’s properties.
Both cadmium (Cd) and tellurium (Te) have specific industrial applications, but their presence in steel can lead to significant issues if not properly managed. While cadmium is sometimes used for protective coatings, its potential to induce brittleness makes it a harmful element in most steel applications. Tellurium, unless intentionally added for a particular purpose, also poses a risk to the mechanical integrity and magnetic properties of steel, particularly in aerospace-grade materials. Therefore, stringent control of both elements is essential to maintaining steel’s performance and longevity.