Copper wire mesh is durable in many types of atmospheres and environments. Although it is softer than a similar stainless steel wire mesh, it is also resistant to atmospheric corrosion but attacked by oxidizing agents such as nitric acid, ferric chloride, cyanides, and ammonia acid compounds. Darby’s copper wire mesh is woven to the industry standard, ASTM E-2016, is 99.9% pure copper and, when exposed to the atmosphere, will naturally develop a thin green layer, known as patina.