Drewgard 315 is a molybdate based corrosion inhibitor for closed cooling systems. It is P & nitritefree and provides exceptional corrosion protection on mild steel and cast iron. It also contains a corrosion inhibitor for yellow metals. Drewgard 315 is not suitable for systems containing aluminum or tin unless the pH is controlled by adding acid. In this case a pH of < 8.3 is required. The product should be used in conjunction with a biocide to control microbiological growth.