HEYN macroetching agent is a chemical preparation whose main components are aqua bidest and copper ammonium chloride. It is used in metallography to detect phosphorus increases in low-carbon steels, which is essential for accurate examination and analysis of the grain structure, weld zones and primary microstructure. It also enables effective grain area etching. Copper ammonium chloride acts as an oxidizing etchant that selectively reacts with phosphorus and certain metal elements, revealing their presence and distribution. The etching time is typically 2 to 10 minutes. After etching, the resulting copper deposit is removed by applying absorbent cotton under water. Due to its specific chemical composition and properties, the HEYN macro etchant enables improved visualization of the microstructure of metals, which increases the accuracy of the resulting analyses and inspections.