Abstract
The inorganic polyphosphates have effectively controlled corrosion, scale and deposits in municipal and industrial waters for the past fifty years. During the first half of this period, the polyphosphates, alone or in combination with other additives, were in the forefront of water management. Over the last part of this period, the polymeric carboxylates and organic phosphorus-bearing compositions have been the primary inhibitor compositions. Presently, the inorganic polyphosphates are being used more widely in combination with the organic inhibitors for control of scale and corrosion in aqueous systems. This trend is related to improved methods of controlling the orthophosphate reversion products of the polyphosphates and reexamination of the special properties of the inorganic polyphosphates.
The inorganic polyphosphates have a broad range of physical forms, solubilities, solubility rates, and molecular weights. They also exhibit good compatibility with hardness metal ions and chlorine. Polyphosphates have useful corrosion and scale inhibition properties in acid waters. In neutral and alkaline waters, threshold concentrations of the inorganic polyphosphates effectively control water-related problems in potable and industrial systems at competitive costs.
