Aluminum and its alloys are commonly subjected to chemical polishing using a solution primarily based on 70% (by mass) phosphoric acid. A typical formulation involves a mixture of phosphoric acid, nitric acid, and sulfuric acid. The composition of the alloy affects the proportions of these acids—sulfuric acid typically ranges from 9% to 15% by mass, while nitric acid varies between 3% and 9%. This process is usually carried out at around 105°C, which leads to the release of significant amounts of nitrogen oxides, posing environmental concerns. To address this issue, a modified method was developed using a phosphoric acid and sulfuric acid base with the addition of S-type copper brighteners, resulting in a yellow-nosed chemical polishing technique. However, this approach is only effective for pure aluminum or aluminum-magnesium alloys and shows limited success on other types of aluminum alloys. Later attempts introduced formulations with just 2% nitric acid, but these did not significantly expand the application range. Despite these limitations, the traditional mixture of phosphoric, nitric, and sulfuric acids remains the most widely used due to its adaptability.
For aluminum alloys with higher copper and zinc content, a small amount of chromic anhydride (2–5 g/L) can be added to improve the polishing results. According to some guidelines, for alloys with high silicon content, a mixture of 60–65 mL/L nitric acid, 15–20 mL/L hydrofluoric acid, and 1–2 mL/L glycerin is often used. This method, however, tends to resemble etching rather than true chemical polishing. Another formulation containing acetic acid is suitable for pure aluminum and 2A12 (LY12) alloys. This method offers a different approach, especially for specific applications where acetic acid-based solutions are preferred. Each technique has its own advantages and limitations, making it essential to choose the right formulation based on the alloy type and desired finish.
High Pressure Hydrogenation Valve
High Pressure Hydrogenation Valve,Dedicated High-Pressure Hydrogenation Valve,High Pressure Hydrogenation Valve Body,High Pressure Hydrogen Solenoid Valve
Chongqing Xingjida Import and Export Trade Co., Ltd. , https://www.xjdvalve.com