Abstract Flow accelerated corrosion (FAC) is a steel degradation that occurs in heat recovery steam generators in the power industry. The mechanism of this corrosion comprises an electrochemical dissolution of the semi-protective magnetite layer (Fe3O4) that is formed within the pipes employed in the boilers. The FAC is influenced by different factors such as fluid velocity, pH and dissolved oxygen concentration. In this context, Rotating Cage tests were used to evaluate the influence of pH and dissolved oxygen content on FAC of A210, P11 and P22 steels. General corrosion was lower for P11 and P22 steels, an effect consistent with the presence of chromium in their compositions. General corrosion was most critical at pH 8.5. The corrosion intensity decreased for the three steels when the dissolved oxygen concentration increased, at 2 m/s. This behavior is coherent considering the most effective precipitation of Fe2O3 inside the pores of the Fe3O4 layer in a more oxidizing environment. For 3 m/s, the corrosion intensity increased for both materials when oxygen increased, showing the shear stress effect. These behaviors were more significant at pH 8.5. About pitting corrosion, the analyzes show localized attack in the majority of coupons, however with very low number of pits.

Flow-accelerated corrosion has been studied by means of computational fluid dynamics (CFD) techniques and rotating cage (RC) autoclave tests according to ASTM G170. This study evaluated through CFD and laboratory tests the influence of RC geometry and baffles on the wall shear stress (τw) proposed by the aforementioned standard. The experimental were performed at 120 °C and 2 angular velocities (500 and 800 rpm) during 25 h in a solution with 600 mg/L of Cl- ions and 10-3 mol/L of sodium thiosulfate. Corrosion rates were obtained by ASTM G31 and the surfaces were evaluated by OM and XRD. Corrosion rate values and XRD analyses showed divergence between samples in different positions in the RC and between distinct regions in the same sample. The numerical simulations and the experimental tests showed a great influence of the baffles on τw. The conservatism in the values obtained with this technique is caused by excessive corrosion close to the samples edges and the non-uniformity of τw on the internal samples surfaces. Thus, the main conclusion of the study is related to the importance of better knowledge on experimental methodology and mathematical approximations for updating the criterion for the correct τw calculation on sample surfaces.

In this work, it is described the design of twenty-four heterocyclic amine-azachalcones compounds through molecular hybridization of chalcone scaffold and fragments of isoniazid, fluoroquinolones, and linezolid with antituberculosis potential. The new compounds were synthesized via Claisen-Schmidt condensation, providing yields of 36-95%. Fifteen compounds showed antituberculosis activity against Mycobacterium tuberculosis H37Rv strain. Two amine-azachalcones 15 and 17 showed relevant biological activity with minimum inhibitory concentration (MIC) values of 6.62 and 4.85 µM, respectively. Compound 12 showed the best profile of antitubercular activity with MIC = 9.54 µM and selectivity index (SI) = 9.33. It was found that morpholine group is important to increase potency of antimycobacterial activity but also to add some toxicity to the chalcone molecular framework. The results described herein would be a guide in the designing of novel and optimized antitubercular derivatives based on the chalcone scaffold.