Anticorrosion coatings with polypropylene

Polypropylene (PP) is utilized as protective coating against corrosion using mainly two technologies application of powder and extrusion. 

The powder is sprayed on the cleaned metal surface by means of electrostatic guns and then the item is placed in an oven at a temperature of about 200°C to melt the powder. With this technology, coating thickness in the range of 100-200 xm can be obtained. In some cases, epoxy primers are used as a first layer to enhance the adhesion properties. 

Alternatively, the metallic item can be heated up in an oven and then dipped in a fluidized bed of modified PP powder a post-heating step may be included. With the fluidized bed process a coating of 200-600 (xm can be applied. The main coating properties are reported in Table 1. As an example of this technology, PP powder is used to coat drums internally, allowing the safe transport of most chemical and foodstuff products. 

Since the 1980s, PP has been introduced in pipeline coating due to its excellent ability to protect the steel against corrosion [1, 2]. The pipeline coating is called a three-layer coating because it is composed of a thin layer of epoxy resin, an intermediate layer of modified PP copolymer and a PP outer layer. 

The function of the epoxy layer is to ensure a strong bond to the steel interface by interacting with its metal oxides. The epoxy has high resistance to cathodic disbondment and high thermal stability its melt-flow behavior facilitates the creation of a thin but uniform film sufficient to fill the anchor pattern in the abraded metal surface. 

---