Corrosion resistance improvement of the Ti6Al4V/UHMWPE systems by the assembly of ODPA molecules by dip coating technique

Living with degenerative diseases, such as arthritis and osteoporosis, is challenging if orthopedic devices manifest adverse effects caused by corrosion processes. Ti6Al4V alloy is used to manufacture orthopedic implants due to its excellent mechanical and osseointegration properties. Nonetheless, it has poor resistance to wear and corrosion by biological fluids and mechanical activity. This degradation process generates the need to improve the corrosion resistance of metallic biomaterials used as biomedical implants. Dip-coating technique is a wet coating method used to lessen wear damage on the metal surface and can produce coatings using a wide variety of molecules at a low cost. In this work, Ti6Al4V alloys were coated with ultra-high molecular weight polyethylene (UHMWPE) and Octadecylphosphonic Acid (ODPA) films forming a UHMWPE/ODPA bilayer coating by dip-coating method to improve protection efficiency against corrosion in phosphate-buffered isotonic saline solutions and proposed it as alternative coatings to delay the failure of medical implants. The optimization of individual coated systems were obtained with an immersion time of 40 s (Ti6Al4V/UHMWPE) and 30 h (Ti6Al4V/ODPA) with corrosion current densities of 1.51 × 10⁻⁹ A cm⁻² and 6.8 × 10⁻⁸ A cm⁻², respectively. The formation of bilayer coatings reduces the average roughness from 19.34 nm (Ti6Al4V/UHMWPE) to 12.67 nm (Ti6Al4V/UHMWPE/ODPA). ODPA deposition on UHMWPE films changes the corrosion rate by interfering with the anodic and cathodic reactions, reducing the corrosion rate to 7.46 × 10⁻⁴ μm y⁻¹ and an estimated corrosion protection efficiency of about 99.99 %. The results show a superior performance as a protective barrier over the individual films (1.19 μm y⁻¹ with 97.2 %, and 0.026 μm y⁻¹ with 99.9 %, ODPA, and UHMWPE, respectively), improving the corrosion resistance of the Ti6Al4V alloys.