Product Short Description: Detect the presence of metallic iron and iron oxide. Chromium and nickel will not be replaced with the Copper sulfate test solution, forming the distinctive copper color on the surface in this 6 minute test. Product Description: The copper sulfate test is used to detect the presence of metallic iron and iron oxide on the surface of materials. Question - What solution strength is needed to copper sulfate solution can be used to determine if a metal is stainless steel or just steel ? Answer - Copper sulfate (CuSO4*5H2O) + H2SO4 (anywhere from 1% to 50% is specified in various test methods).