What is Iron Phosphatizing

Iron phosphatizing is a conversion process where the metal surface being treated actually reacts with the phosphatizing compound to form an insoluble, non-metallic coating on the surface of the metal.

Why Phosphatize?

Each section of metal has numerous small centers of positive and negative charges, referred to as anodes and cathodes, caused by stresses in the metal and high concentrations of carbon. These centers, when moisture and oxygen are present, act like a battery and galvanic corrosion results.

The insoluble phosphate coating bonded to the metal surface is non-conductive and insulates the positively and negatively charged “pockets” from each other. Thus, due to the fact that the phosphate coating is relatively insoluble and acts as an insulating barrier, the process of corrosion or galvanic corrosion is retarded, but not eliminated.

The phosphate coating increases the surface area of the metal with these peaks and valleys and since the coating is rough, provides for mechanical adhesion of the film applied to it. For this reason, phosphatizing provides better adhesion and corrosion protection of liquid and powder coatings.

Iron phosphatizing processes

Iron phosphate coatings can be applied using (3) different methods. The method of choice is dependent upon the parts to be processed.

Spray washing – This process is limited to the physical size, weight and configuration of the parts to be processed. It is not practical or cost effective to Phosphatize large parts using the spray wash method.

Immersion – The immersion process also has the same limitations of size, weight and part configuration as the spray wash process. This method is most commonly used for batch phosphatizing of smaller parts.

Manual steam gun phosphatizing – This process is the only method that can be considered for Iron Phosphatizing large parts, components or equipment with electrical components that cannot be subjected to large amounts of aqueous contact. Sioux offers custom steam cleaners to meet the needs of this method of Iron Phosphatizing prior to the application of liquid or powder coatings.