*3.1.1 Chromate programs*

The chromate programs are based primarily on the zinc and chromate mixture, with the ratio of CrO4 <sup>2</sup><sup>−</sup>: Zn2+ from 6:1 to 8:1, and the chromate reserve varies from 10 to 25 ppm. If low or ultralow chrome program is employed, the ratio of CrO4 <sup>2</sup><sup>−</sup>:Zn2+ is typically 1:1, and the chromate reserve is from 3 to 8 ppm, respectively. In order to lower the health and environmental hazard by chromate, polyphosphate, phosphonate, or polyacrylate is often added as well. The level of zinc or other possible inhibitor is correspondingly raised for compensation.

A typical "standard" formulation for a chromate product that may be used as shown in **Table 3**, for example, in a large coastal petrochemical facility, is described here. This program formulation will tend to be dosed continuously to achieve a 35–50 ppm product reserve in the recirculating cooling water. The pH of the cooling water is typically 6.0–7.0.
