Development of Corrosion Protection Coating System for Aerospace Grade Aluminum 7075 Alloys

Abstract

Aluminum Alloys are used in Aerospace and Automobile Industries due to their high strength to weight ration and their ease of formability but there are limitations pertaining to the corrosion protection of the alloys. Presently, Chrome based coatings are applied to Aluminum Alloys but due to their carcinogenic nature, efforts are being made to explore alternates. This work presents the exploration of a potential alternate of Chrome Conversion Coating for the enhancement of corrosion resistance of Al-7075 alloys. Nickel Phosphorus (NiP) based coatings show good corrosion resistance and Boron Nitride (BN) nanoparticles (a refectory material) can be used as an appropriate addition. BN was incorporated in NiP using a simplified coating bath and well optimized parameters. A comparative analysis was carried between BN based NiP and without BN based NiP along with different percentages of BN addition (0.5 ~ 2.0 %). The detailed analysis of the developed coating was carried out via Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), Nano-Indendation, Micro Hardness, Tafel Scan and Electrochemical Impedance Spectroscopy (EIS). All the results are of the evidence that there is a continuous rise of corrosion protection up to 2.0% and this makes BN as suitable reinforcement for NiP Coating on Aluminum Alloys.