Copper is the most noble of metals and should always avoid being in contact with dissimilar metals, unless there is barrier between. When dissimilar metals are in contact with each other in the presence of oxygen and moisture, the lower grade metal will corrode. Therefore, should only be installed with fasteners and extrusions made of stainless steel or copper. Special machining and fabrication guidelines need to be taken into consideration due to the unique metallurgical properties of copper.