# Microscopic Analysis of Structure and Wear for Metallic Materials Using SEM
## 4 Conclusions  
Using SEM, the microscopic analysis provided important information about the structure, purity, and wear of the metal materials from which the examined pipes for the aqueous medium were made. This information is crucial for their evaluation and prediction of degradation that shortens the lifetime of pipes. The results from the evaluation of samples for seamless steel pipes confirmed that the process of corrosion was mainly on the surfaces and the internal surfaces of pipes in service, and there were noticeable deposits from the aqueous flowing medium. The surface (external and internal) of sample No. 1 had a relatively large roughness, which characterized the production process of this unused pipe. The sample designated as No. 2 showed intercrystalline corrosion, cracks, and material peeling from the internal surface after 20 years of use in a hot water heating system. The oldest pipes--pipes used in a hot water heating system for 48 years and more (samples designated as No. 3 and No. 4) had a decarburized subsurface area and there was the occurrence of inclusions based on sulfides and aluminates on the internal side of surface. The knowledge obtained from the research of the materials for pipes for the water medium provides valuable information that is necessary for the design, production, and maintenance of metal components in the hot water heating system. Based on the knowledge gained, we recommend the following:  
* The regular inspection and maintenance of metal hydraulic elements, especially those that interact with the water medium;
* The evaluation of currently used materials for the production of water pipes with regard to their resistance to corrosion and wear, depending on the specific application;
* The implementation of appropriate coatings/paints and protective insulation to reduce the risk of atmospheric corrosion and mechanical wear;
* The monitoring of the development of wear over time;
* The regular control of the water medium, thermal conductivity values, occurrence of chemical elements, and water pH. These recommendations will help to prevent unwanted problems associated with the degradation of metal materials and low-quality functioning of the heating system and ensure their long and reliable service life under real operating conditions in relation to hot water heating. The obtained results also show that seamless steel pipes can reach the prescribed service life of 50 years. An important factor affecting their service life is the flowing medium and its temperature, hardness, conductivity, and pH. Attention should also be  
Figure 12: Detail of internal pipe surface (500\(\times\) zoom) of sample No. 4 [7]. paid to laying pipes through ceilings, walls of building structures, and assembly channels or shafts, where atmospheric and bacterial corrosion very often occurs. However, damage to the material structure on the external and internal surfaces leads to their replacement (reconstruction), sometimes even earlier than after reaching this service life. In practice, we encounter such cases more and more often. The summary of the obtained results points out that the revealed undesirable aspects are interconnected, and it is necessary to see connections between them that can warn the customer (user) against a wrong decision. If corrosion degradation is considered primary in these systems, everything around it is essential. In conclusion, we can conclude that any poor quality of the material (surface roughness, fine surface cracks, incipient corrosion before assembly) or technological error during joining (thermal influence of the material after welding, stress states after pressing, etc.) will be manifested by non-functionality or non-functionality, or even at the end of the life of the device, structure, or some installation elements.