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Having low investment cost and simple operating, dip application iron phosphate coating process is the traditional process mostly preferred.


Metal surface has to be cleaned from grease and possible oxidations prior to phosphating. If there is too much rust in the surface, acid pickling must be employed. Metal workpieces coming out of acid pickling bath must be rinsed with water properly to prevent drifting of acidity. Balance of the phosphatizing bath can be broken up if excessive driftings come from pickling bath.


Phosphate coated workpieces are treated with passivation solution and then are brought to drying stage at maximum degree of 110 °C. Over 110 °C, phosphate film begins to deform.


Important parameters are ;

*   Temperature

*   pH

*   Concentration

*   Application time


Immersion type iron phosphate conversion coating bath must work around 50 – 55 °C with application time between 5 – 10 minutes. Concentration varies % 1 to % 5. In the course of time, pH and Total Acid point of  the coating composition has to be controlled. Generally pH is tended to increase. To prevent high pH, pH reducer must be added to phosphating bath until reaching to optimum level.


Concentration of the coating bath is controlled by additional chemicals. Eventhough all phosphatizing products have characteristic Total Acid values, generally it must not stay below pH 6 in points.