Oxygen Cell Corrosion is the most common corrosion in a fire sprinkler system. Oxygen Cell Corrosion is caused by oxygen in water reacting with wet iron metal. The corrosion byproducts are brown and orange rust, which are known as ferrous and ferric hydroxides. These iron hydroxides can cause mill scale type layers to form. These type deposits are primarily found in dry fire sprinkler systems. In wet systems oxygen cell corrosion produces tubercles which will reduce water flow and/or even clog fire sprinkler pipes. Once oxygen is almost depleted it will produce hydrogen that will react with chlorine or sulfates. This reaction produces hydrochloric or sulfuric acid within the tubercle. Ultimately pinhole leaks will occur within the tubercle due to acid attack.