This reduced limescale buildup caused by boiling hard water. They are commonly used as descaling agents to remove limescale deposits. Phosphates bind calcium and magnesium ions to prevent 'hard-water' type limescale deposits. It is used to remove and discourage the buildup of limescale from boilers and evaporators. Some kettles have built-in filters, primarily to reduce limescale buildup. Examples of oilfield scales are calcium carbonate (limescale), iron sulfides, barium sulfate and strontium sulfate. It is widely used to dissolve limescale. The process of limescale build up in a kettle in hard-water areas is similar. Descaling agents are commonly used to remove limescale. It flows over rocks and plants and they become covered with limescale. Limescale may foul the system over time and require periodic acid cleaning.