Phosphate coatings cathodic treatment

In some cases and in particular for steel substrates, a relation between the mean delamination rate and the potential difference between the defect and the intact interface has been observed (Stratmann et al., 1996). As the potential of the defect is fairly constant, the potential difference is determined by the potential of the intact interface and for some systems increasing stability of the interface has been observed for a decreasing potential of the intact interface. Therefore, for some systems of technological importance (cathodically primed steel), the potential of the intact interface has been analyzed as a function of the pre-treatment, the deposition conditions, and the curing temperature of the polymer (Klopfer, 1996). A typical result is summarized in Fig. 7-71. The potential of the untreated steel is compared to the potentials of the phosphated and the phosphated and polymer-coated steel. In... 

The possibilities include control of the environment (perhaps by humidity control, de-aeration, or addition of inhibitors which retard the cathodic process) and control of the surface (by surface coatings, electroplating or producing surface layers of high resistance, as in the phosphate treatment of steels). There are also two more purely electrochemical methods. 

---