The Arnao manufacturing facility is located approximately 4 km west of the San Juan de Nieva Smelter. Zinc oxide is produced in distillation columns fed with zinc skimming and metallic residues and scrap from the San Juan de Nieva smelter. Lead/Silver anodes for electrolytic cells are manufactured and their convenient maintenance is undertaken in this plant.

Arnao was the site of an old zinc smelter which worked for about 100 years since the 1850’s. When the smelter closed in the 1950’s the refining section was reconverted into a zinc oxide production facility. Other zinc semis manufacturing facilities were installed at Arnao and were transferred later to San Juan de Nieva except the oxide production facility and the rolling mill.