Removal of Organic and Inorganic Contaminants from Titanium Turning Scrap via Alkali and Acid Two-Step Cleaning

For the recycling of titanium turning scraps, residual cutting oil and tool abrasion particles must be removed from the surface. In this study, a novel surface treatment was developed to remove cutting oil and tool abrasion particles by cleaning and drying titanium scrap using the two-step process of alkali cleaning-acid cleaning. The surface residues before and after cleaning were compared through SEM, confirming that tool abrasion particles were removed thoroughly via acid cleaning. Elemental analysis and thermogravimetric analysis of titanium scrap confirmed that most of the cutting oil was removed by alkali cleaning, and XPS analysis confirmed that tool abrasion particles embedded on the scrap surface were removed by acid cleaning. After dissolving the scraps to make an ingot, the microstructure and tensile strength were measured. It was confirmed that acid cleaning after alkali cleaning provides the optimal condition.