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Method for Determining Intergranular Corrosion of Aluminum Alloys
Intergranular corrosion (IGC) is a type of corrosion that primarily occurs along grain boundaries in aluminum alloys. This type of corrosion occurs when certain alloying elements as well as nonmetallic inclusions are exposed to a corrosive environment. It is important to understand the various methods used to identify and evaluate the intergranular corrosion rating of aluminum alloys to ensure that the most appropriate material is used in manufacturing processes.
In 1987, the National Standard of the People’s Republic of China (GB 7998-87) established a method for determining intergranular corrosion of aluminum alloys. This method of evaluation is often referred to as the weighed double acid-salt (WDAS) method. The WDAS method is used to determine the intergranular corrosion of a metal in order to assess its suitability for further use.
The WDAS method is a two-part process. The first part involves the determination of the metallic grain size. This is done by weighing a small sample of the metal and then suspending it in a 0.5N sodium chloride solution. A standard solution of 0.5M hydrochloric acid and 0.05M sulfuric acid is then added. These components are allowed to react for 10 minutes. Following this, the sample is removed, washed thoroughly, and left to dry. Once dry, the remaining grain size is determined by counting the particles under the microscope.
The second part involves the determination of the intergranular corrosion rate. A sample is collected from the parent material, oxidized in air (80℃, 2h), and then suspended in a 10% oxalic acid solution (60℃). This solution is then mixed with distilled water and allowed to react for 24 hours. The corrosion rate is then determined by weighing the sample again and calculating the percent weight loss.
In summary, the GB 7998-87 method is a two-part process used to determine the intergranular corrosion of aluminum alloys. This two-part process involves the determination of the metallic grain size and the determination of the intergranular corrosion rate. This method is an important and effective way to evaluate the suitability of a metal for further use.
