Influence of different pretreatments on Ti-6Al-4V surface integrity and scratch-resistance of epoxy coating: Analysis of topography, microstructure, chemistry and wettability

The improved scratch resistance of epoxy-based coatings on titanium alloy is greatly needed in the current biomedical device sector. Due to commercial factors, this improvement must be either non-consumptive or inherited from the antecedent machining steps. This study contributes an extensive understanding of Ti-6Al-4 V surface topography, microstructure, chemistry and wettability generated with various processes, such as milling, polishing, hydrofluoric acid-etching and micro-blasting with different process parameters by utilizing optical and electron microscopy, energy-dispersive X-ray spectroscopy, X-Ray diffraction and surface tension. The phenolic resin is then spin-coated, cured and scratched with a conical indenter in a constant loading mode. The influence of roughness parameters, microstructural and chemical changes on wettability and delamination size, pattern and mode are analyzed. The root mean square gradient of surface slope and the developed interfacial area ratio are found to be in good correlation with the delamination factor. The delamination factor and specific traction force after micro-blasting are improved by a factor of two compared to that achieved by polishing or milling and is superior to that obtained by acid-etching. This study, therefore, clearly demonstrates the strong potential of micro-blasting as a pretreatment technique to enhance the adhesion strength and scratch-resistance of epoxy coating on titanium implants.