Minimization of hazardous substances in metallographic analysis
09. Aug 2022
Achieving equivalent results with less use of hazardous substances: In the metallographic analysis department, the focus is increasingly on minimizing hazardous substances. This is because initial results from etching tests with various materials show: Very good results for analysis can be achieved even with low concentration chemicals.
Metallographic analysis is primarily concerned with the investigation and description of different materials and their changes. For example, metallic materials and lightweight materials are prepared and examined using light microscopy and electron microscopy. In this way, different surface structures and layers, but also 3D measurements of different material surfaces can be created and analyzed.
However, very dangerous chemicals, such as hydrofluoric acid, are sometimes used for metallographic examinations - e.g. for etching polished specimens to analyze the microstructure. This requires special precautions as well as constant vigilance and care in everyday work. In order to prevent accidents and to achieve greater safety in everyday work, the first series of tests have now been carried out in which an etchant with a lower concentration was used. In one of the tests, an austenitic sample was first treated with two classic etchants, one consisting of 60% nitric acid and the other with a solution of 100 ml hydrochloric acid and 10 ml nitric acid.
In the alternative, reduced-pollutant etching method, only 1 ml nitric acid and 1 ml hydrochloric acid were then used for comparison. Despite the considerably lower concentration of hydrochloric acid and nitric acid, comparatively good analytical results were obtained with the alternative etching. On the one hand, good contrasting of the grain boundaries and the twins was observed. On the other hand, the delta ferrite was visibly etched out. In further etching experiments with the materials Ti6AlV4 and AIMgSi0.5 (ENAW-6060), highly hazardous chemicals, such as concentrated nitric acid and hydrofluoric acid, were replaced with alternative hazardous minimizing substances, such as hydrogen peroxide and potassium hydroxide, and clear results were obtained.
The research series of the department is thus promising that in the future a hazardous substance-reduced work in metallographic analysis may be possible in a permanent and standardized way.