Surface treatment is mostly required during and after heat treatment to remove oxide scales and various contaminants on the metal surface, reduce the activity of the bare metal surface, and apply a protective layer and various functional coatings on the surface of titanium and its alloys. Surface treatment must also be carried out before and during the coating process. This coating is applied to improve the properties of the metal surface, such as preventing corrosion, oxidation and wear.
The pickling conditions of titanium and its alloys are determined by the type (characteristics) of the oxide layer and the existing reaction layer, and the type of this layer is affected by the high-temperature heating process and the increase in processing temperature (for example, forging, casting, welding, etc.) .
Only a thin oxide layer is formed at a lower processing temperature or a high heating temperature of about 600X or below. Under high temperature conditions, an oxygen-rich diffusion zone is formed near a certain oxide layer, which must also be eluted by acid. In addition to this oxygen-rich diffusion layer. Various descaling methods can be used: mechanical methods to remove thick oxide layers and hard surface layers, descaling in molten salt baths and pickling in acid solutions to remove scale.
