Zinc is introduced into water naturally by the erosion of minerals from rocks and soil most zinc is introduced into water by artificial pathways such as by-products of steel production coal-fired power stations or from the burning of waste materials. Zinc is also used in some fertilizers that may leach into groundwater. Zinc is used as a corrosion inhibitor for Cooling water. The AE305 – ZINC TEST KIT is easy to use and the results achieved are fairly accurate.