In the middle of heat treatment and after heat treatment, surface treatment is mostly required in order to remove the oxide scale and various contaminants on the metal surface, reduce the activity of the surface of the bare metal, and apply protective layers and various functional coatings on the surface halogen of titanium and its alloy Surface treatment is also performed before and during the coating process. The coating is applied to improve the performance of the metal surface, for example, to prevent 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 temperature during the processing (for example, forging, casting, welding, etc.) . At a lower processing temperature or about 600X: only a thin oxide layer is formed under the heating temperature of the following high temperature, and an oxygen-rich diffusion zone is formed near a certain oxide layer under high temperature conditions, which must also be eluted by acid In addition to this oxygen-rich diffusion layer. Various descaling methods can be used: mechanical methods for removing thick oxide layers and hard surface layers, descaling in molten salt baths, and acid elution descaling methods in acid solutions.
In many cases, a combination of several methods can be used, for example, the mechanical scale is removed first and then the pickling is combined, or the salt bath and the acid washing are combined to remove the scale. In the case of the oxide layer and the diffusion layer formed at a higher temperature, a special method should be adopted. However, the oxide layer formed under the condition of high temperature heating to 600X: can be dissolved away by general acid washing.