Enhanced Corrosion and Wear Behavior of Nano Titanium Carbide Reinforced Polyurethane PMC Coating on Aluminium 7075

Abstract

Aluminum 7075 has an extensive variety of utilization over different fields because of its intrinsic properties such as high ductility, high toughness, high strength and low density. It is being utilized broadly for structural parts in aviation industries to manufacture aeroplane wings, internal bearing and fuselage. In spite of having high strength to weight ratio, aluminium does not have good resistance against wear and corrosion.Surface coating technology is a well-known technique for improving the wear resistance and corrosion resistance of the coated substrate which can eliminate corrosion along with fretting and adhesive wear by providing suave surface..Generally, polyurethane (PU) coatings were done on engineering metals to provide corrosion protection; hence it is highly advantageous to coat it on aluminium 7075 to improve its corrosion resistance.Polyurethane coating technology offers excellent adhesion and corrosion resistance when compared with other traditional metal coatings such as electro plating, electroless plating, PVD, CVD etc. Polymer Matrix Composite (PMC) coatings were preferred to improve the wear resistance along with corrosion resistance on corrosive and low wear resistant metals such as copper alloys, mild steel, and aluminum alloys. In this paper, PMC coatings of polyurethane as matrix along with nano titanium carbide reinforcement were coated on Aluminium 7075 through physical deposition method. The nano TiC was blended with Epoxy polyamide (EP) and Polyurethane separately in different proportions (1%, 2% and 3%) with the help of mechanical stirrer. Epoxy polyamide along with TiC nano composite was first coated as a base coat on the Aluminium 7075 substrate at the pressure not exceeding 35bar. The polyurethane was coated as top coat along with nano titanium carbide as reinforcement on Aluminium 7075 in different volume percentage. Wear, corrosion and optical microscope studies were done. Micro hardness test reveals that the sample which was coated with 3% nano TiC along EP and 3% nano TiC & PU gives the highest hardness when compared to other samples. It is attributed to the fact that it contains the highest percentage of titanium carbide mixed to both the polyurethane and the epoxy polyamide when compared to the other samples which has nano TiC in either base coat or upper coat. Similarly, through salt spray test it was found that highest corrosion resistance was observed in the sample which was coated with nano TiC in both the EP and PU. The samples were also examined through optical microscope and test results were justified. The inclusion of nano titanium carbide to the polymer coating increases the coating hardness, wear resistance and corrosion resistance of the aluminium 7075.