Types of Zinc Phosphates

Because so many variations of zinc phosphates are available, it is convenient to divide them into groups for discussion. Although no formal classes of zinc phosphates exist, they have been divided here into groups or generations, more or less by chronological development. 

The usefulness of first-generation zinc phosphate is limited by its low solubility [62] only a small concentration of phosphate ions is available to protect the metal. This is a problem because corrosion inhibition by phosphates takes place only when the anion concentration is higher than O.OOIM in a salt solution at pH 5.5 to 7.0 [57]. 

Relative Solubilities in Water of Zinc Phosphate and Modified Zinc Phosphate Pigments 

Source Bittner, A., J. Coat. TechnoL VcA. 61, No. 777, p. Ill, Table 2, with permission. 

Second-generation zinc phosphates can be divided into three groups basic zinc phosphate, salts of phosphoric acid and metafile cations, and orthophosphates. 

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