Nitric Acid and HF Mixtures
Nitric Acid + HF (hydrofluoric acid) Mixtures Solutions. Titanium is best etched with blends of HF and Nitric, 3% HF is very common and etch rates increase as Nitric Acid concentrations are increased. Etching titanium with hydrofluoric acid is a slow process and produces a by-product of hydrogen gas. It also produces a rough surface finish. The addition of nitric acid increases the etching rate, eliminates the formation of hydrogen gas, and produces a smoother surface finish. Without the nitric acid present, the titanium surface is very rough and nodular. As the nitric acid concentration increases, the surface roughness decreases to the point of creating a surface that is almost reflective. In essence creating a slight electro-polished surface.