Protective Coatings for Polymer Composites

Thermal spray coating is being studied as one of the techniques used for coating graphite reinforced polymer composites, which are extensively used in the aviation industry. These coatings are studied for improvement of surface properties such as erosion resistance, UV protection, property retention and electro magnetic shielding. NiAl (63:35) (65%Ni,35%Al) intermetallic, NiAl (95:5) (95%Ni,5%Al), Aluminum and Zinc coating were thermal-spray deposited using different procedures (plasma, flame, electric wire arc) onto composite specimens. Two categories of coating were evaluated: Coatings with bond coating and coatings without bond coating. These coatings were tested for protection against erosion encountered by aircraft components. The microstructures and micro-hardness of these coatings were determined. The bond strength between the substrate and the coating layer was evaluated by means of adhesion tests. The results obtained are discussed, with special attention being paid to the specific characteristics of the different spraying procedures.