Recycling of Stainless Steel – Limits and the Effect of Copper Content

6. 11. 2025

Stainless steel is one of the most important engineering materials today. It offers high mechanical strength, long service life, and—above all—exceptional corrosion resistance. A major advantage is its ability to be recycled repeatedly, contributing to sustainability and efficient resource management.
Although stainless steel can be recycled almost indefinitely, the process is not without challenges. One of the most critical limiting factors is the presence of copper (Cu).

Copper content in stainless steel
In standard stainless steels, copper is usually present only in trace amounts (typically less than 0.3%). However, in recycled scrap it can enter from various sources—most commonly from electronic waste or highly alloyed specialty steels.
Unlike carbon or sulfur, copper cannot be removed from molten steel by conventional metallurgical processes, which means it accumulates over time and can deteriorate material performance.

Effects of increased Cu content in stainless steel
Excessive copper content directly affects stainless-steel properties:

• Structural weakening: Copper tends to segregate along grain boundaries, making the steel more brittle and more prone to cracking.
• Impact on surface treatment: Copper can adversely affect pickling and passivation—processes essential for forming a compact chromium oxide (Cr₂O₃) passive layer that provides corrosion resistance. Elevated Cu content can cause defects in this passive film, increasing susceptibility to localized corrosion.

Prevention and control
To ensure the quality of recycled stainless steel, it is essential to:

• perform precise scrap sorting,
• analyze chemical composition during melting, and
• limit the use of materials with excessive Cu content to specific alloys where copper is desired or permitted, such as austenitic steel EN 1.4539, duplex steel EN 1.4501, and other special grades.

Recycling of stainless steel plays a key role in the circular economy and in sustainable industry. However, its technological limitations must be respected. Copper content significantly influences not only mechanical properties but also corrosion resistance and the overall reliability of the final material.
Therefore, systematic control of chemical composition is essential to ensure that recycled stainless steel meets all relevant standards and specifications.