Having low investment cost and simple operating,
application iron phosphate
is the traditional process
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
and then are brought to drying stage at maximum degree of 110 °C.
Over 110 °C, phosphate film begins to deform.
Important parameters are ;
Immersion type iron phosphate conversion coating
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
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.