Surface Engineering, Anti-Corrosion Materials, Failure Analysis

The common failures mechanisms of boiler components at elevated temperatures and monitoring techniques used in power plants to detect damaging or failures are generally well described in literature. Despite of different classification concerning the principal failure mechanisms of boiler thermal power plant components, it is necessary to emphasize that essential difference between these classification does not exist. Concerning the different failures mechanisms it is obvious that the most of them are completely explained and clear in physical sense of process but some of them are not still so explicit. Therefore, until today there is a great interest to investigate the failures of power plant boiler components especially having in mind the all peculiarities of particular events. This efforts are necessary while a full assessment of the failure mechanism(s) is required to prevent further failures due to the same causes. The numerous case studies presented in this paper were done as a contribution to this efforts.

steels in three different corrosive media: distilled water, tap water and 3 % NaCl water were analyzed. Scanning electron microscope (SEM) of wear particles were acquired, forming database for further analysis. This study shows that there is no remarkable difference in the particle size with test solution. However, the frequency distribution of particle sizes differed with the test solution. It is the highest at small sizes for tap and distilled water. While for salt water, it is the highest for the larger sizes (larger than 50 μm). All the particles, irrespective of solution, manifested similar morphological features such as lamellar shape, crack propagation on the particle surface and secondary cracks. This indicates that the particles are produced by a single mechanism, namely, fatigue. With regard to the role of corrosion in the development of cavitation erosion, it was most pronounced in the case of salt water. It was found that dissolution of ferrite acts as areas of stress concentration which give rise to crack initiations. This gives a strong impetus to the crack initiations.

The inhibitive efficiency of extracts from some plants parts against corrosion in metals has been well proved. Moreover, it's been established that nanometer scaled materials exhibit more distinct properties compared to the bulk materials, and nanoparticles has high inhibition efficiency due to their large surface to volume ratio. We therefore investigated the corrosion protection potentials of copper nanoparticles derived from potato leaf, stem and roots on duplex stainless steels (2101 and 2205) in 0.5M H 2 SO 4 solution using Autolab PGSTAT 204 potentiostat. Atomic Absorption Spectroscopy, Ultraviolet Visible Spectroscopy and Fourier Transformed Infrared Spectroscopy were used to characterised the extracts. The results indicated that the corrosion rate decreases with an increase in inhibitor concentration. The studies showed that the inhibition efficiency of the nanoparticles increases with the concentration. It was also observed that the nanoparticles from root offered the highest resistance to the dissolution of the metal in acidic environment when compared with nanoparticles from the leaves and the stems. The copper nanoparticles inhibited 2101 and 2205 duplex stainless steel in 0.5M H 2 SO 4 .